TS-3229: filter unsupported epic plugin metric names

Epic can't deal with all our metric names, so just drop metrics
that don't match it's naming conventions.
epic: add more gauge names
TS-3230: remove unused ink_error APIs
TS-3231: use CoreAPI Reconfigure from traffic_manager

When traffic_manager gets a SIGHUP, use the Core Reconfigure() API,
rather than hitting the local manager directly. Rename the Core
Diags() API to not conflict with ink_diags Diags() macro.
TS-3231: remove SIGUSR2 handling from traffic_manager

SIGUSR2 causes traffic_manager to log a stack trace using
ink_stack_trace_dump(). However, ink_stack_trace_dump() calls
alarm(3), which will make us exit with SIGALRM.
TS-3231: remove superfluous fileBinding class
TS-3231: add the proxy.node.config.reconfigure_time metric
TS-3231: add the proxy.node.config.reconfigure_required metric
TS-3231: track when process restarts are required

Start checking the record update type when we process reconfiguration
events so that we can publish metrics to tell the operator when a
restart is required. Note that is is only as accurate as the
RecordsConfig definitions, so YYMV.

Add the following new metrics:
  proxy.node.config.restart_required.proxy
  proxy.node.config.restart_required.manager
  proxy.node.config.restart_required.cop
TS-3231: mark proxy.config.body_factory.template_sets_dir reloadable

The body factory templates are reloaded in HttpBodyFactory::reconfigure()
so mark them as RECU_DYNAMIC so we don't think that we need to
restart on every reconfiguration event.
TS-3232: remove obsolete proxy.config.cache.vary_on_user_agent configuration
TS-3233: allow traffic draining before restart

Add the --wait option to traffic_line. This option delays the
corresponsing bounce or restart until the number of active client
connections drops to the threshold given by the
proxy.config.restart.active_client_threshold configuration variable.