fetch2: wget add _check_latest_version_by_dir

fetch2: wget add _check_latest_version_by_dir

Add _check_latest_version_by_dir this function provides support
for scan every directory newer than current dir in order to get
latest_versionstring, example:

	http://somedoamin.com/project/v2.1/
	http://somedoamin.com/project/v3.0/

Change return of _vercmp from True/False to -1/0/1 to provide test
when current directory is equal to newer directory this helps to
scan the same directory to get minor versions, example:

	http://somedoamin.com/project/v2.1/project-v2.1.2.tgz
	http://somedoamin.com/project/v2.1/project-v2.1.6.tgz

Signed-off-by: Aníbal Limón <anibal.limon@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>