Remove the need to have a mainfile.php in the distribution.

With a little prodding from Mamba and a little consideration, there is no apparent valid reason that the mainfile.php whould be part of the source or distribution. This will eliminate the mainfile.php overwrite disaster (or the accidental commit) that anyone using XOOPS seriously has managed to do, at least once ;)
Merge pull request #38 from geekwright/master

Remove the need to have a mainfile.php in the distribution.