Installer: Add perm tests for directories that must be writable
Installer: Add perm tests for directories that must be writable

This commit adds additional permission test lines to the
checkFolderPermissions method in MGRequirementsHelper. There are
several subdirectories in uploads/ that must be writable by the mg
program when running; the existing check on the uploads/ directory is
insufficient to verify that these directories are also writable.

tiltfactor/mg-game,tiltfactor/mg-game,tiltfactor/mg-game,tiltfactor/mg-game,tiltfactor/mg-game