Added publishing tags by file publisher

[IzabellaRaulin]

Summary of changes:

• added publishing tags by file publisher
• added exemplary task manifest with tags section

Testing done:

• running mock_tagged-file.json and confirm that metrics published to /tmp/snap_published_mock_file.log contain this tags

Before:
/tmp/snap_published_mock_file.log

2016-06-03 16:29:17.907943193 +0200 CEST|/intel/mock/bar|The mock collected data! config data: user={root} password={secret}
2016-06-03 16:29:17.907946183 +0200 CEST|/intel/mock/foo|The mock collected data! config data: user={root} password={secret}
2016-06-03 16:29:17.907949792 +0200 CEST|/intel/mock/host0/baz|87
2016-06-03 16:29:17.907957581 +0200 CEST|/intel/mock/host1/baz|71
2016-06-03 16:29:17.907958358 +0200 CEST|/intel/mock/host2/baz|88
2016-06-03 16:29:17.907959743 +0200 CEST|/intel/mock/host3/baz|86

After this change:
/tmp/snap_published_mock_file.log

2016-06-28 16:25:21.774951286 +0200 CEST|/intel/mock/host1/baz|70|tags[os:linux; experiment:1; plugin_running_on:devmachine]
2016-06-28 16:25:21.774953488 +0200 CEST|/intel/mock/host2/baz|67|tags[experiment:1; os:linux; plugin_running_on:devmachine]
2016-06-28 16:25:21.774954979 +0200 CEST|/intel/mock/host3/baz|73|tags[experiment:1; os:linux; plugin_running_on:devmachine]

@intelsdi-x/snap-maintainers

[marcin-krolik]

@IzabellaRaulin Maybe we could add tags in little bit different style
2016-06-22 10:52:37.631772944 +0200 CEST|/intel/mock/host2/baz|7777|experiment: exp 11; os: linux

[IzabellaRaulin]

Thanks @marcin-krolik . What do You think about something like that:
tags[os:linux; experiment:1; plugin_running_on:devmachine] - this style might be more clear

[candysmurf]

LGTM