Dialog classes moved into one file - dialogs.py

    Other changes:
- Previous files with dialog classes deleted
- Dialog classes now in the dialogs.py
- Little bit resized wizard window
- Added some comments to wizard class
- Bug fixed that Dialog and FileDialog objects wasn't creating (added imports)
- Instead of button "Next" on last page now there is "Finish" button
- Remade "Changelog" dialog - looks more user-friendly
- Added subtitles to wizard's pages
- Deleted unnecessary attributes on pages (labels)
package_builder.py: fixed function calls
Albert didn't fixed method name calls
moved dialogs.py to new structure
fixed errors in __init__.py catched by pyflakes
implemented plugin engine (fix #11)
added forgotten file from commit aaa40ff
removed class Predictor
changed doc of plugin_engine according to new plugin API
added loading of plugins
added more plugin declaration files
Merge branch 'master' of https://github.com/rh-lab-q/rpg

Conflicts:
	rpg/package_builder.py