project manager - add checkbox to use non-standard directory

[johrstrom]

I think we need a checkbox here that enables and disables the directory field here.

I think this because it's likely not apparent to users that when left blank the system will use generate a default. I.e., they won't know that blank is a valid setting.

So, let's add a checkbox that's something like override default directory that will then enable this field. Checking the box will enable directory override and enable the directory field when unchecking the box will disable the field and use the default directory.