This allows for having multiple co-maintainers for AUR packages.
Co-maintainers have push access to the package base Git repository but
are not allowed to change the package base category, disown the package
or modify the list of co-maintainers. The primary maintainer of an AUR
package can edit the list of co-maintainers from the Package Actions
box.
Implements FS#17911.
Signed-off-by: Lukas Fleischer <archlinux@cryptocrack.de>
