Display error message if BEE2 is installed in the P2 folder

[vrad-exe]

Some people download BEE2 and install it to Portal 2/bee2/, not realizing that this is used as the BEE2 search path when exporting. Rather than letting this happen, resulting in a cryptic "access denied" message appearing later when exporting/compiling, BEE2 should detect this on startup and display a message that it needs to be installed somewhere else, then exit.

[flarn2006]

This is exactly where I was planning on installing it. Glad I saw this.

[flarn2006]

Actually isn't this a duplicate of #1258? Did you forget you posted that one?

[vrad-exe]

Yeah it is, I wish TeamSpen would implement this because people do this really often and it's easy to deal with...