* Sensors: refactor configuration

- move sensor implementaion to the .ino,
  remove dependency undef / define from sensor files
- update test/build/sensor.h from SENSOR_SUPPORT
- allow to change sensor config variables externally
- `#include <...>` for global headers and libraries,
  fix relative path for math library

* add missing sns <-> i2c dependency

* ledrelay should return relay_none as default

* rollback to original test header

* include debug header when requested (relative)

* Added T6613

* Added T6613

* Added T6613

* Added T6613

* Added T6613

* Added T6613

* Added T6613

* Added T6613

* Added T6613

* Updated copyright string

* Buffer from 6 bytes to 8 bytes

Current gcc-4 does not mark this as warning, but gcc-9 notices the 3 char size requirement. Buffer should be 8

* Use 5000ppm max

* travis: move build flags tests outside of hardware header

* mqtt: fix typo

* travis: use files instead of bundling test cases into script

* fixup! travis: use files instead of bundling test cases into script

* fix variable expansion, remove custom h at the end

* add ade7953 to sensors list

* custom.h path as variable

* shellcheck

* fix printf syntax, silent again

* fix bash 4.3 treating empty array as unset variable