Get and Create TSMeta by metric name and tags.

Follow up to https://github.com/OpenTSDB/opentsdb/pull/219

Now based off the next_lastdp branch, using the TSUIDQuery class. Creation of TSMeta object via HTTP possible. Must be enabled by specifying create=true in the URL. Now also initializes the counter when a TSMeta is created explicitly.

Please have a look at the counter initialization, whether this is done right.