Factored substitution tokens out of the main code so that the user ...

can add their own.

Added logic to autodetect whether the Restructured Text installation uses ...

the ".py" suffix for the "rst2*" programs.  This is not consistent across
platforms and thus has to be handled for portability.

Fixed typo that prevented TMPDIR from getting set. ...

Moved TMPDIR to .mkprojectrc.
Create project destination directory if it does not exist.

Ensure projects directory exists.

Added support for user-specific configuration via USERCONFIGDIR in .mkprojectrc.

Initialize revision number

Initial revision