Updated Urza's org locations.

Updated the file and directory references to point inside the Dropbox
directory for Urza.
Set the org agenda files on feymarch.
Added habitrpg submodule.
Added note about Tramp git repo.
Added ledger mode.

The files for ledger mode were copied from the ledger source code.  Ledger
itself is in a Git repo, but the Emacs mode is in a subdirectory of that
repository.