* Initial concept for pluggable storage (sans tests and docs)
* Add TLS storage docs, test harness, and minor clean up from code review
* Fix issue with caddymain's temporary moveStorage
* Formatting improvement on struct array literal by removing struct name
* Pluggable storage changes:
* Change storage interface to persist all site or user data in one call
* Add lock/unlock calls for renewal and cert obtaining
* Key fields on composite literals
