Removed unused stats modules from v3 and v4 backends.

Stats are now handled directly in v3/v4 flow modules.
Refactor v4 queue infrastructure + tests.
Proper decrementation fo dscp_remark meter band
Merge branch 'dev' of github.com:FlowForwarding/LINC-Switch into dev
Refactor v3 queue infrastructure + tests.
Merge branch 'dev' of github.com:FlowForwarding/LINC-Switch into dev
Fix to sys.config and main linc supervisor.
Merge branch 'master' into dev
Add missing v3 port function.
Fix tests after queue refactoring.
Fix bug with improper handling of
actions:apply_list/2 return value.

In both v3 and v4 versions, instructions module
was improperly matching on return value from
actions:apply_list/2. Bug was unnoticed because
actions module was mocked in instructions unit
tests. Now we don't mock actions module anywhere
to avoid such hidden bugs in the future. 
Unit tests speedup.

Extracted meck initialization/teardown to happen
only once per test suite in the setup/teardown
functions. Initializations of other fixtures are
handled for each test case separately.
Fix dialyzer warnings (not all of them).
Fix action validation in v3 and v4 flow module.
Merge pull request #56 from FlowForwarding/dev

Late night fixes for LINC 1.0