[METRICS-383] write_tsdb plugin
Uncrustify write_tsdb
[METRICS-383] Add HostTags which adds tags for all metrics from this writer
[METRICS-390] Add tag writing from metadata using TSDB target_set patches
[METRICS-390] Fix string handling for TSDB prefix and tags
[METRICS-390] Make sure HostTags is initialized if not configured
Merge pull request #630 from llnw/F-METRICS-383-tsdb-writer-5.4

write_tsdb plugin