- replace JustWifi with a custom WiFi module
- re-implemented Core methods that deal with scanning, directly work with the SDK callback
- re-implemented Core method for opmode to avoid dealing with the 2.7.x pseudo modes
- re-implemented Core method for forced-(modem)-sleep (with the intention to merge with OpmodeNull... todo)
- disable reconnect and autoconnect from SDK, avoid unintentionally storing ssid & pass for these and
  make connection routine watch for events instead. timeout is implemented as a local timer
- do not store runtime data that can be retrieved via SDK calls
- settings are loaded only when starting AP or STA, networks are no longer kept in memory
- settings STA ssidN must be unique
- remove char buffer from the event callback
- trigger station-disconnected event when actually disconnected, not when connecting or explicitly requesting it
- generic rssi sorting method for initial connection, do rssi checks while connected to find a better network

Drop (temporarily?) wps and smartconfig. Both are implementable with the new approach,
but come with some weird expectations from the SDK side (no extra heap with wps, broadcasting plain-text
passphrase with smartconfig, storing station config implicitly, etc.).

Both are sort-of fixed with RTOS SDK, but it is still a big question of whether to support them at all in the current state.

Namespace build configurations of modules, make more things into constexpr
(not fully finished though)

Unify code using ...Count() to parse IDs

Avoid using unsigned char aka uint8_t as index, prefer size_t
as most code already uses it anyway. Making sure we never accidentally
truncate the value or try to read it as 32bit-wide. Also, simplify
access to built in containers, since those use the wide type as well.

Renames led and button types, more consistent initialization and field access.

- shrink utils source file, move heartbeat and boot management into system
- improvise with 'heartbeat' functionality. include scheduler implementation that will
manage the per-module heartbeat callbacks with individual 'mode' and
'interval' settings. current ones are mqtt (including relays, lights, thermostat), debug and
influxdb. preserve heartbeat NONE, ONCE and REPEAT, REPEAT_STATUS is effectively a hbReport & status bit.
- mqtt heartbeat is managed through mqttHeartbeat() callbacks
- tweak mqtt callbacks to use lists instead of the vector, slighly reducing the size of the .bin
- update WebUI, include report setting and update hbMode values
- make sure general.h settings include new heartbeat,
move constant definitions outside of the header
- correctly include dependencies through the .cpp, avoid leaking
internal details.
- as a side-effect, base headers are no longer included recursively

- 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

* support GPIO setting in WebUI
* experimental led pattern support
* support loading settings in setup() (not yet fully working)

- use similar to relay & wifi, configuration through helper methods that
  use indexed defines
- clock cycles for led delay polling
- button mode defaults