fetch2: remove localcount and use AUTOINC instead

fetch2: remove localcount and use AUTOINC instead

- do not use the BB_URI_LOCALCOUNT database for computing revision
incremental numbers anymore
- sortable_revision now generates "AUTOINC+${latest_rev}"
- use one incrementing value rather than several
- PV becomes 0.1+gitAUTOINC+deadbeefdecafbad_decafbaddeadbeef
- remove all localcount code and simplify the fetcher
- this patch addresses the following proposal:
http://lists.linuxtogo.org/pipermail/bitbake-devel/2012-November/003878.html

Signed-off-by: Constantin Musca <constantinx.musca@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>