Expose cache lifetimes to config; make default lifetimes longer

Currently salesforce module uses 2 different cache lifetimes for short- and long-term cache.
Short term is 300 seconds, and long term is one day.

Both these can probably be longer, and their values should be exposed to config with some way to clear them manually.
This can help reduce api calls for things that don't change often, e.g. Describe()