CC: version.mk and image-config.in: adjust to 15.05.1

CC: version.mk and image-config.in: adjust to 15.05.1
* Adjust the default version number in include/version.mk to 15.05.1
* Copy the correct download repo location from include/version.mk
  to base-files/image-config.in

After the change to version.mk, new builds made from CC sources will
have opkg config that downloads from the recent 15.05.1 packages repo
instead of the ancient 15.05 packages repo.

The change to image-config.in ensures that if somebody uses
VERSIONOPT config options in .config, he will get the
correct download repo address (instead of trunk snapshots).

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>
git-svn-id: svn://svn.openwrt.org/openwrt/branches/chaos_calmer@49053 3c298f89-4303-0410-b956-a3cf2f4a3e73