implemented remove in mwc-src

Implemented the "remove" command in mwc-src, allowing the user to remove
sources from the repository. Also switched to the new relativePath() and
normalizePath() functions. What's still missing is the ability to add/remove
entire directories using mwc-src.
added mwc-src dir add and remove --all

mwc-src now supports adding entire directories of source files. If one of the
arguments is detected to be a directory, all *.mw files in that directory are
added to the repository recursively. The "remove" command gained a "--all" flag
which allows all sources in the repository to be removed.