Add pt script

The `pt' script is used to add a command-line interface to the
`project-template' module. It runs the
`pt-create-project-from-template' function, passing along the first
and second arguments.
Change variable delimiter

Since the `__' is used quite a lot in, for example, Python code and
files it proved to be a sub-optimal as a delimiter. Now, by default,
`$!' is used, which should appear somewhat less (I hope) and it has
been made customizable. Look out when customizing, it is placed in a
regular expression without any escaping.