some unfinished code related to sensor settings synchronization
fixed bug with groups creation
Sensors configuration is now synchronized properly
added .txt to gitignore to stop spamming with usability statistics
Merge branch 'master' of https://github.com/qreal/qreal into sensors-synchronization

Conflicts:
	plugins/robots/robotsInterpreter/details/d2RobotModel/d2ModelWidget.cpp
Fixed too frequent sdf files re-reading
fixed styleguide
Merge pull request #1204 from qreal/sensors-synchronization

Sensors synchronization + Some optimizations for sdf-based icons
Physics engine moved into strategy class
Added simple physics engine implementation
Added switching between engines in 2D model ui
Merge branch 'master' of github.com:qreal/qreal into physics

Conflicts:
	plugins/robots/robotsInterpreter/details/d2RobotModel/d2ModelWidget.h
	plugins/robots/robotsInterpreter/details/interpreter.cpp
	plugins/robots/robotsInterpreter/details/interpreter.h
Merge pull request #1207 from dvvrd/physics

Switching between physics engines in 2D model
Version incremented to 2.5.2
Merge pull request #1208 from dvvrd/robots

QReal:Robots 2.5.2
Russian C generator included into intstallers
Merge pull request #1209 from dvvrd/robots

Russian C generator included into intstallers
Fixed do-while cycle in trik and russian c generators
Worked arround a bug with setting edge`s pos to nan.
Fixed some bugs of inserting node into edge
Made generators working in merged if inside merged if case