Batching support for Monasca Log API

Monasca Log API supports posting single log entries at a time today. This is inefficient when a client/agent is chugging through a log file that has thousands of log entries.
Need to add batching support so that a client can batch multiple log entries and send to the server in a single request.
This would be comparable to the metrics API, for example.

It needs to be decided (in the mid-cycle meetup) if this can be done as part of the existing API or a new API. Also, it needs to be decided if we should stick to a common JSON content-type instead of having to support both plain-text and JSON.