Add convenience method for constructing a Resource for a package in the default locale.
Add convenience methods for converting seec::Resource directly to wxString.
Add rudimentary checks to determine if an XML document is an augmentation.

Add methods to get the user local augmentation directory, and to load an augmentation directly from a wxXmlDocument.
Add augmentations panel to preferences.

At the moment this just allows the user to download an augmentation from a
given URL. The augmentation file is loaded immediately and saved into the
user's local data directory for augmentations.