* Enforce Minimum cache size for transit backend
* enfore minimum cache size and log a warning during backend construction
* Update documentation for transit backend cache configuration
* Added changelog
* Addressed review feedback and added unit test
* Modify code in pathCacheConfigWrite to make use of the updated cache size
* Updated code to refresh cache size on transit backend without restart
* Update code to acquire read and write locks appropriately
This massively simplifies transit locking behavior by pushing some
locking down to the Policy level, and embedding either a local or global
lock in the Policy depending on whether caching is enabled or not.
* Start work on passing context to backends
* More work on passing context
* Unindent logical system
* Unindent token store
* Unindent passthrough
* Unindent cubbyhole
* Fix tests
* use requestContext in rollback and expiration managers
