Because --enable-application is the current way to do things, transpose
it to configure.py, but since --enable-application=js doesn't make
sense, make it an alias of a new --enable-project option.
This only partially moves --enable-application out of old-configure.in
because there are a lot of other things intertwined with it.
A new configure option --with-devtools (which sets MOZ_DEVTOOLS) is added to
control whether all DevTools, just the server, or no DevTools are included.
This defaults to just the server.
Applications should also include /devtools within their moz.build tree, so that
DIST_SUBDIR is in effect for all DevTools files if it is used by the app.
Mike Hommey
Alessio Placitelli
J. Ryan Stinnett
Ted Mielczarek