Added parameter value classes to miror descriptions.

Enabled compilation in main cmakelist.
Updated schema to handle slicer command line plugins.

Updated CMakelists. Exported module reader class.
Fixed include statements.
Fixed warnings.
Cleanup interfaces and make Slicer xsd the default.
Added a XML schema for QtDesigner UI files.
Improved the CLI XML schema.
Simplified parsing of CLI XML descriptions + cleanup.
Added a XSL for transforming the CLI description to a UI file.
Added alternative way for "parsing" a CLI XML description.

Instead of parsing it, we transform it using a XML stylesheet. The
result is a valid Qt UI file which can be dynamically loaded at
runtime. Support classes take care of validating and transforming
the files.
Merge branch 'fix-ctkPathLineEdit-initialization' into HEAD

* fix-ctkPathLineEdit-initialization:
  Fixed an initialization bug in ctkPathLineEdit.
Sample app to create a GUI for a CLI module.
Added skeleton for two CLI modules.
Disable old ModuleDescription tests using old API.
Renamed library and sample app for CLI module support.
Renamed CLI files and class names to have more descriptive names.
Use consistent command line arguments.
Made ctkCmdLineModuleDescription and related classes read-only.
CLI API prototype with a new separate QtGui dependent library.
Implemented getting a ctkCmdLineModuleDescription object.