WIP on tim/issue-messages-3258
Merge branch 'tim/3266-identifier-format' into tim/issue-messages-3258

Conflicts:
	src/clustering/administration/issues/log_write.cc
	src/clustering/administration/issues/name_collision.cc
Improve error messages for log write, name collision, and server down issues.
Merge branch 'reql_admin' into tim/issue-messages-3258

Conflicts:
	src/clustering/administration/issues/name_collision.cc
Improve error message wording based on feedback in code review.
Merge branch 'tim/issue-messages-3258' into next