Add of enabled flag for pluggable wares

* Added enabled flag for simulators, generators and observers
* Cleaned code
Update of Firespread example simulators

* Updated spatial graph information in signature

(references OpenFLUID/openfluid#20)
Model and monitoring management in OpenFLUID-Builder

* Added basic coupled model management
* Added basic monitoring management
* Added display of signatures

(references OpenFLUID/openfluid#246)
Add of parameters management for wares in OpenFLUID-Builder

(references OpenFLUID/openfluid#246)
Reorganization of source code files in OpenFLUID-Builder

* Moved common files from base subdirectory to common subdirectory

(references OpenFLUID/openfluid#246)
Introduction of a graphical view of models in OpenFLUID-Builder

(references OpenFLUID/openfluid#246)
Add of variables IO in graphical view of models in OpenFLUID-Builder

* Added simulators and generators grahics, with IO slots
* Added connectors representing variables

(references OpenFLUID/openfluid#246)
Add of variables names in model view in OpenFLUID-Builder

* Added variables names as connectors labels
* Cleaned code
* Added model view options

(references OpenFLUID/openfluid#246)
Export of model view to files in OpenFLUID-Builder

* Added export to image (PNG format)
* Added export to vector (SVG format)

(references OpenFLUID/openfluid#246)
Add of items in model and monitoring management in OpenFLUID-Builder

* Added simulator selection dialog
* Added generator creation dialog
* Added observer selection dialog
* Updated placement of items in model view
* Added icons for wares status
* Cleaned code

(references OpenFLUID/openfluid#246)
Add of parameters management in model and monitoring in
OpenFLUID-Builder

* Added parameter dialog
* Cleaned code

(references OpenFLUID/openfluid#246)
Add file system watchers for wares in OpenFLUID-Builder

* Added dynamic update of wares availability
* Cleaned code

(references OpenFLUID/openfluid#246)
Wares watching preferences and confirmation dialogs in OpenFLUID-Builder

* Added confirmation dialogs when removing wares or parameters
* Added preferences for confirm/not confirm
  of wares and parameters removals
* Added preferences for enable/disable wares watchers

(references OpenFLUID/openfluid#246)