Add autogen.sh file

This is based on gnome-shell autogen.sh. It also fetch gvc submodule if needed
Merge pull request #18 from efernandesng/master

Add autogen.sh file
applets/menu-window: Fix segfault when applications change
Use modal dialog attachment to parent by default
applets/clock: No longer use seconds

The use of seconds causes constant resizes and changes to the panel,
which is a complete waste of cycles. It also has the adverse effect
of changing the border size, visually changing with each update.
Merge remote-tracking branch 'upstream/master'