Modified a bit the behaviour of UserDefinitionDialog when clicking on
apply/save buttons

wx.Dialog

viewer are no longer plugins.
Improved significantly the ergonomy of the periodictable viewer
The user can now performs several atom selection and transmutation.
Improved the atom list widget
Fixed several bugs
Added new icons

viewer
Bug fix when closing a lugin pane
Bug fix with DL_POLY converter plugin

The DataInfoPlugin is now OK
Bug fix with pubsub.sendMessage wrong keyword
Improved the AtomListSelectionDialog
Removed unuseful pubsub calls from the molecular viewer

Relocated several packages

Bug fix that was making the sphinx-build very slow

Bug fix in UD_STORE

Modified the Singleton class to get rid of module import path problem

Moved the converters to a specific menu
Reintroduced the __setitem__ for the ElementsDatabase
Reintroduced and refactored the PreferencesSettingsDialog
Refactored the PeriodicTablePlugin
Added new icons
Refactored the Icon class

conflicts
Refactored many GUI related module to make the main app restartable