Spin out mapcache package from implementation

Spin out mapcache package from implementation

We will need SimpleMapCache in both implementation and southbound, hence
splitting out the mapcache package from implementation as its own
bundle. As a result MappingMergeUtil needs to be split into two part,
with a small overlap. Some config values are rewritten as constants
until a proper configuration infrastructure is in place, or we at least
spin out the config package too.

Change-Id: Iff6aaeb79a2e310e62c343aa2ca6d5fc868e5a94
Signed-off-by: Lorand Jakab <lojakab@cisco.com>