Adding Split navigation support.

Two new tags added to the Theme SDK - %top_navigation% and
%sub_navigation%
Updated Documentation

- Renamed the v1.0 doc to just documentation.markdown
- Updated the SDK Readme.
Linebreaks++
Update documentation.markdown
Updates Documentation
Updates Documentation
Updates example theme for RW6 theme syntax.
Renames example theme to use RapidWeaver 6-only file extension

Developers wishing to use split navigation in their themes should
ensure their themes are named .rapidweavertheme as this will ensure
they are installed in RapidWeaver 6 only.
More docs updates.
Adds Custom.css to encourage theme overriding instead of outright modification.

- Removes RWTheme ShippedInVersion key as this is a private key
intended for Realmac Software use only.
- More documentation.
- Updates modification date.
Adds details about the Addon Support URL
Updates order of docs.
More documentation changes.
Removing Last-Updated Dates

They’re a pain to keep updated when GitHub shows this just fine…
Link work?
Links++
-Updates PLIST key for Support URL
Adds New RWAddonAuthor key

- Documents deprecation of RWThemeAuthor key.