fix graceful shutdown bug

add base CA

enable graceful shutdown

POST support, error handling fixes, and graceful shutdown

support relabel_config in servergroups to return different label valu…

…es per-target

add lifecycle option + remote_write_exporter, consolidation/cleanup i…

…n remote_read/servergroups

upstream prometheus API client

metric rename

Add remote_write Appender

use relabel_configs labels in servergroup returned series