Fixed `winfo` macro.
Added logging macro for error messages.
Removed forced CMake configuration options.
Fixed include dirs CMake variable inclusion.
Ensured file and project deps were in order.

  * Added a GUI IDE project label.
  * Ensured that sources were automoc-ed by Qt4.
Added documentation to plugin macros.
Improved plug-in library discovery.

  * Fixed UUID conversion to sane ID string.
  * Ensured full Linux path discovery for libraries.
  * Introduced more documentation.
Updated logic for plugin interface detection.
Updated plugin code.

  - src/Wintermute/plugin.cpp
    * Updated ctor with new private arguments.
  - src/Wintermute/private/plugin.hpp
    * Added logic for loading plug-in binaries.
    * Added logic for obtianing plug-in interfaces.
Added macro for Wintermute plugin declaration.
Moved logic for plug-in loading into prv data.
Used a `dynamic_cast` instead of `qobject_cast`.
Adding some wise cracks into the docs.
Merge branch 'feature/extensibility' into develop

* feature/extensibility:
  Used a `dynamic_cast` instead of `qobject_cast`.
  Moved logic for plug-in loading into prv data.
  Added macro for Wintermute plugin declaration.
  Updated plugin code.
  Updated logic for plugin interface detection.
  Improved plug-in library discovery.
  Added documentation to plugin macros.
  Ensured file and project deps were in order.
  Fixed include dirs CMake variable inclusion.
  Removed forced CMake configuration options.