#4356: SourceBrowserMenu class implementation

1) added SourceBrowserMenu class with some helpful functions:
* connectActionByName() - connect action with name to some specific
slot. If no action with name found, no connection established.
* getActionByName() - return pointer to QAction object with name you
specify as an argument. If nothing found, returns 0.
2) Implemented SourceBrowserMenu's tools and function to another classes
which used old-style QMenu.
#4356: Code improvement

Some simple and obvious stuff.