Accept spaces before (UN)CACHE, more helpful error message.

This is most helpful when running a series of statements
using -e, when adding spaces increases readability.
Add console logging about reloaded RDDs.
Merge pull request #249 from kayousterhout/cache_generosity

Accept spaces before (UN)CACHE, more helpful error message.
Merge pull request #251 from kayousterhout/reload_log

Add console logging about reloaded RDDs.