Improve CMake with SFML's one
Add abiltiy to compile for Android
Re add BUILD TYPE to CMake
Compile to a static library now
For Android, files are install to sources/sfml-ui instead of sources/sfml
The library is now working on a NDK project (but not usable)
Add support on touch events for AbstractButton and Button
Fix SFML_INCLUDE_PATH and SFML_LIBRARY_PATH not considered as PATH
Add support on touch events for TextField
Backspace doesn't work and text is entered twice, seems to come from Android SFML's port
Add sf::ui::ButtonTouchedEvent
Merge tag 'v0.4.1' into feature-android

Conflicts:
	src/UI/CheckBoxGroup.cpp
Add getFormat() non-const for FormattedTextField
Merge branch 'master' into feature-android
Improve project structure
Use FindSFML CMake module
Add doc genereation, similar to SFML's one
Merge branch 'master' into spinner
Adapt spinner to the new structure