Move tunnels from workers to separate package

Move tunnels from workers to separate package

Tunnels package provides implementation of simple data forwarding
tunnels between IP addresses pairs.

The implementation has been moved from workers package and adjusted
to newly defined Tunneler interface. The interface defines basic
operations on tunnels (creation, getting address, closing).
It provides additional layer of abstraction allowing mockuping tests
of parts of the code using tunnels.

The mock implementation of interface is provided in matcher package.
It is generated using mockgen command:

mockgen	-package matcher \
	-destination=matcher/tunneler_mock_test.go \
	-write_package_comment=false \
	git.tizen.org/tools/boruta/tunnels Tunneler

Change-Id: Ida42f0134f0c365c8f1ffe772b859a0218c301ed
Signed-off-by: Lukasz Wojciechowski <l.wojciechow@partner.samsung.com>
Signed-off-by: Maciej Wereski <m.wereski@partner.samsung.com>