Local Cache + Sanity Checks

[krowvin]

Working on issue #34 it dawned on me that we could cache the parameters, intervals, and other various metadata in a local store.

Then on every TSID built, for example, raise a warning if a user is requesting a TSID with a parameter that doesn't exist in CWMS.

Perhaps base the cache on a time interval or a version of Repgen.

Additionally could add a flag that lets you disable cache

Ie

--disable-cache