Fix of header guard in config.hpp.in

* Replaced __CONFIG_HPP__ by __OPENFLUID_CONFIG_HPP__

(closes OpenFLUID/openfluid#449)
Split of single CPack config file into OS specific files

(closes OpenFLUID/openfluid#450)
Introduction of multiple workspaces

* Updated preferences for multiple workspace
* Added management of multiple workspaces in preferences dialog
* Added generic widget for paths management 
  (list widget with add, remove, move up, move down buttons)
* Refactored and cleaned code

(closes OpenFLUID/openfluid#448)
Major refactoring of ui components

* Renamed guicommon namespace into ui::common and ui::market namespaces
* Added config file for ui components
* Moved common components and resources from Builder into ui namespace
* Moved common tools from Builder to tools namespace
* Refactored and cleaned code

(closes OpenFLUID/openfluid#453)
(closes OpenFLUID/openfluid#455)