Integration of market client in OpenFLUID-Builder with Qt

* Added the market client classes
* Added icons in resources
* Added launch of market client for OpenFLUID-Builder

(references OpenFLUID/openfluid#246)
Introduction of translations management in OpenFLUID-Builder with Qt

* Added translations files
* Added translations management in PreferencesManager
  and PreferencesDialog
* Added translations builds in CMake build system  
* Added script tool to create/update translations files
  from source code
* Cleaned code  

(references OpenFLUID/openfluid#246)