Добавлено выделение редактируемого лэйбла по f2

По нажатию F2 при выделенном блоке должно включаться редактирование
первого редактируемого лейбла на сцене для этого блока
Edited selection of the label by pressing F2
Merge branch 'master' of https://github.com/artbez/qreal
changed code in conformity with stylegide
fixed a bug
Supported attribute "override" for ports.
Small remarks in supported "override"
Supported attribute "override" for ports.
merge branches and removal conflicts
merge branches [2]
supported generalizations for "pictures" and "labels"
Merge branch 'master' into override
some modifications for "label"
Merge pull request #1289 from dvvrd/robots

Some bugfixes for TrikStudio a8
multiple inheritance and changes in styleguide
repair "}"
small changes
small changes for "Override"
changes for "override"
with consts