Make it possible to permanently remove servers by deleting from rethinkdb.server_config.
Merge branch 'reql_admin' into tim/2873-permanently-remove
Update pre-reql_admin integration test for permanently removing servers.
Overhaul server_down and server_ghost issues so that they don't do weird things with servers that have been permanently removed.
WIP on tim/3256-invalid-config-issue
Change how issue filtering works; improve server_ghost_issue description message.
Merge branch 'tim/2873-permanently-remove' into tim/3256-invalid-config-issue
Add table_needs_primary and data_lost issues.
Merge branch 'reql_admin' into tim/3256-invalid-config-issue

Conflicts:
	src/clustering/administration/servers/server_config.cc
Fix some bugs; remove some debugf()s.
Add comment.
Fix minor stylistic issues; use reconfigure() to fix broken tables instead of fixing them manually.
Merge branch 'tim/2873-permanently-remove' into reql_admin

Conflicts:
	test/interface/dead_server_issues.py