Various fixes and improvements in OpenFLUID-Builder with Qt

* Fixed wrong return value when creating project
* Introduced real button box in new project dialog
* Added specific CMake configuration for Mac OSX
* Added official OpenFLUID icon in resources

(references OpenFLUID/openfluid#246)
Import feature when opening a project in OpenFLUID-Builder with Qt

* Added tool for recursive copy of directory contents
* Added mouse cursor set to wait when necessary
* Added clickable URL link in home widget

(references OpenFLUID/openfluid#246)
Recents project menu in OpenFLUID-Builder with Qt

* Added menu for recent projects
* Added limit for maximum number of recent projects

(references OpenFLUID/openfluid#246)
Recents project home panel in OpenFLUID-Builder with Qt

* Added list of recent projects
* Added class for label management of recent project
* Fixed recent projects list management

(references OpenFLUID/openfluid#246)
Run simulation dialog in OpenFLUID-Builder with Qt

* Added simulation worker thread and listener
* Added simulation dialog
* Cleaned code

(references OpenFLUID/openfluid#246)
Add of a CMake switch to disable the build of GTK based apps and libs

(references OpenFLUID/openfluid#246)