Converting geocouch to CMake.

The following CMake targets exist:

"geocouch" -just compiles the geocouch source, using rebar as
always. ("make all" is the default, and "all" depend on "geocouch", so
"make" by itself will compile the source.)

"geocouch_makecheck" - same as old "compileforcheck" target.

"geocouch_check" - same as old "check" target; cleans, runs
geocouch_makecheck, and then runs the tests.

"realclean" - same as old "clean".

I specifically did not include .tar.gz or "dist" targets as they
support the old, undesirable way of creating source tarballs.

Change-Id: I9098c47db8b50fdde760130391b529f987e74d03
Reviewed-on: http://review.couchbase.org/35099
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: Volker Mische <volker.mische@gmail.com>
Reviewed-by: Chris Hillery <ceej@couchbase.com>
Tested-by: Chris Hillery <ceej@couchbase.com>