- (experimental) provide generic way to read magnitude values
- expose /api/metrics with values formatted specifically for prometheus, with relay and sensor data
- small tweaks to sensor init

Example config:
```
scrape_configs:
  - job_name: 'espurna'
    metrics_path: '/api/metrics'
    params:
      apikey: ['apikeyapikey']
    static_configs:
      - targets: ['espurna-blabla.lan:80']
```
Where ESPurna side has
```
apiKey => "apikeyapikey"
apiEnabled => "1"
```

- general conversion from .ino modules into a separate .cpp files
- clean-up internal headers, place libraries into .h. guard .cpp with _SUPPORT flags 
- fix some instances of shared variables instead of public methods
- tweak build system to still build a single source file via os environment variable ESPURNA_BUILD_SINGLE_SOURCE

* Fixes and updates for thermostat and display:

- Switch to original esp8266-oled-ssd1306 library
- Fixes and updates for thermostat and display
- Add display switching off after interval
- If THERMOSTAT_DISPLAY_SUPPORT enabled, then one click enable display, long click switch relay. This functionality also depend on fix for long click. See pull request https://github.com/xoseperez/espurna/pull/2172

* Move buttons definitions for display to dependencies.h

* Pin ThingPulse/esp8266-oled-ssd1306#3398c97

* Config: remove prototypes.h

* fixup order

* word

* add missing

* fix warning while still using .ino

* bad at c/p;

* ntp: try using sntp app from lwip, drop ntpclientlib

* fix display

* thermostat: fix day and month getters

* test build sizes with scheduler

* use system timers for once-a-minute scheduling, no polling

* tick

* avoid timestamps, use tm

* drop utc rpn operator, add utc_hour and utc_dow

* try to build with old implementation too

* dep

* notify ws

* progmem

* cleanup types

* offset tm values by 1 to match existing schedules

* avoid using ntpclientlib with rpn

* test. show debug strings in sch

* fix secureclient

* consts, fix unsyncing when changing tz (and not triggering sntp after reinit for some reason)

* startup time in seconds

* same delay as lwip

* header

* assume build timestamp is unixtime

* cache server value

* fmt

* typo

* handle dhcp request

* rename

* web

* TZ.h

* add notice about what alias means

* fix disabling NTP_SUPPORT

* scheduled ticker

* same behaviour as old module

* rollback rpn dependency check, utc_ prefixes

* ...

* comments, refactor naming

* experimental: refactor get/set/del/hasSetting

* sensors

* lights

* cleaup

* r

* tuya

* fixup! sensors

* fixup! tuya

* header defaults types

* fix lights

* setup already checks for max

* helper for flashstring

* fix overload

* oops

* refactor includes

* warnings

* test with migrate

* add ids in a separate file

* cleanup

rev: crash

rev: domoticz

rev: encoder

rev: loopdelay

rev: hass

rev: i2c

rev2: hass

rev: mqtt

rev: rfm69

rev: relay

rev: rpn

rev: settings setup

rev: hb settings

rev: telnet preprocessor fix

rev: settings wrap

rev: tspk bool style

rev: wifi types

rev: util hb

rev: settings

fixup! rev: settings

* rev: cleanup wifi injections based on new getters

* hasSetting now can return true for empty key

* show hardcoded network in web

* oops

* fix ws referencing wrong index

* ensure empty strings are written

* c/p

* use experimental schema style for payload, mark network as not deletable

* allow to customize converter

* shorter syntax, try using with wifi

* use proper #if syntax to handle definitions that are missing

* fixup ota sc checks getter, cast schEnabled to bool

* add utils header to sensors

* Test: check core feature build

* order

* add missing

- mask is defined as (relay# status << number)
- transparently handle base-2 and base-10 numbers
- if the relay mode requires us to save the mask, it will be saved as base-2

* Core 2.6.0+ fixes

* fix env -> config, run travis04 job

* don't duplicate free heap in frag data, use single stats struct

* fix dtostrf warnings, bump buffer sizes

* ...and even less words for fragmentation stat

- update every dynamicjsonbuffer with fixed size constructor argument
- change to ws callback registration to use a class builder (just cosmetic)
- test multiple ws data callbacks for each module
- remove some of the static strings in favour of ws data callback
- improve sensor ws callback data size, remove duplicated strings
- use static buffer in wsDebugSend
- postpone wsSend until loop, implement wsPost to allow other modules to queue message callbacks. remove Ticker based ws callbacks for data
- update WebUI files

* Add "Enable Thermostat" switch

* Add heater/cooler thermostat mode