Forced each message to have declared type as parts of Bus logic
depends on it and previously we encountered undefined
behaviours. Added tests and messages validators.
* Timers now are Application thread safe
* Timers now have consistent API independend of Application (no more c style timers)
* Timers can have either: callback or override onTimer() method - this
way we can create more complicated timers or just use existing ones
* gui::Timer added via adapter class GuiTimer to decouple sys::Timer
with gui::Timer
* Fixed race in wrapper
* Updated docs
* fixed using std and cpp_freertos and DataReceivedHandler hidden in Application.hpp
Till now there was no clear way to register hanlder for message in
Service, with this approach one can register function/lambda handler
for Message which encurages handling messages in functions rather than
in hudge switch cases.
With aproach like this our Messages resembe something between Command
and State pattern. In state pattern `Message` would be `Event` send,
whereas Service would be `Context`.
