Tidy: Purge old-lua & quazip dirs, fix file perms, rename a doc. file, excl. shadow-build dirs from git

Quazip is not used anymore as is old-lua stuff, so is removed.

Many files have the unix execute permission bits set (probably not being respected
by Windows OS environment utilities) which may hinder Qt install functionality (it
does not like moving files with those bits set which are not the target application).

In preparation for possible shadow building ./build-src-* should be excluded from
git consideration by addition to .gitignore file.

The Mudlet API reference file in html format had a redundant "_HTML" in the file
and had incorrect pathname in mudlet::show_help_dialog().

Signed-off-by: Stephen Lyons <slysven@virginmedia.com>