fix extension checking

git-svn-id: svn://svn.icculus.org/fs2open@10553 387891d4-d844-0410-90c0-e4c51a9137d3
separate generation of automatic nodes into its own file, and fill in the GOG install node

git-svn-id: svn://svn.icculus.org/fs2open@10554 387891d4-d844-0410-90c0-e4c51a9137d3
fix bug with an automatic node not being checked if it's a child node

git-svn-id: svn://svn.icculus.org/fs2open@10555 387891d4-d844-0410-90c0-e4c51a9137d3