Syntax error fixed: #include <QPushbutton> -> #include <QPushButton>
Issue #66 fix : Selection rectangle non-modal
Merge pull request #95 from slima4/master

fix Issue #89
Merge pull request #96 from mbg033/master

#Issue 66 (non-modal selection rectangle) + syntax error fixed in layerwidget.cpp
sync
Merge remote-tracking branch 'upstream/master'
hide checkbox OpenGL
small fix
added OpenGL in LayerWidget