linux CustomHvac for MQTT support

[krzysiekbielicki]

This is my dirty way to enable basic MQTT support in Hvac channel

[krzysiekbielicki]

I have no experience in C++ co it's ugly copy-paste, but works!

Purpose of this PR is to enable MQTT as output from Hvac.

In my solution I have multiple temperature sensors connected to supla-device via MQTT and tasmota relays in heat source and valves (work in progress) this allows me to depend only on local network not on active internet connection and still use cloud

[klew]

Please update sd4linux readme file with "CustomHvac" description. Please also add there yaml config example.

cpplint is failing on those:
extras/porting/linux/linux_yaml_config.cpp:1024: Lines should be <= 80 characters long [whitespace/line_length] [2]
extras/porting/linux/linux_yaml_config.cpp:1024: Missing space before { [whitespace/braces] [5]
extras/porting/linux/linux_yaml_config.h:157: Lines should be <= 80 characters long [whitespace/line_length] [2]
extras/porting/linux/supla/control/custom_hvac.cpp:32: Lines should be <= 80 characters long [whitespace/line_length] [2]
extras/porting/linux/supla/control/custom_hvac.cpp:34: Single-parameter constructors should be marked explicit. [runtime/explicit] [5]
extras/porting/linux/supla/control/custom_hvac.cpp:44: Namespace should be terminated with "// namespace Supla" [readability/namespace] [5]
extras/porting/linux/supla/control/custom_hvac.cpp:49: Weird number of spaces at line-start. Are you using a 2-space indent? [whitespace/indent] [3]
extras/porting/linux/supla/control/custom_hvac.cpp:52: Weird number of spaces at line-start. Are you using a 2-space indent? [whitespace/indent] [3]
extras/porting/linux/supla/control/custom_hvac.h:41: Single-parameter constructors should be marked explicit. [runtime/explicit] [5]
extras/porting/linux/supla/control/custom_hvac.h:43: Line ends in whitespace. Consider deleting these extra spaces. [whitespace/end_of_line] [4]