Add ValidMatcher with tests

Add ValidMatcher with tests

ValidMatcher is a Matcher interface implementation for handling events
related to validation of requests after ValidAfter time is passed.
It matches pending, ready to be run requests with idle workers that are
capable to fulfill request capabilities and belong to group for which
request owner has rights.

Tests base on using MockRequestsManager, MockWorkersManager
and MockJobsManager for mocking up RequestsManager, WorkersManager
and JobsManager interfaces.

Change-Id: Ib654f1ef276eecb14dc4ad3114afcccd83a7bf5d
Signed-off-by: Lukasz Wojciechowski <l.wojciechow@partner.samsung.com>