Handling exceptions at core level itself + bugfix

* Conversion to milis can result in either a null ptr exception (if the
  timestamp passed is null) or a illegal arg exception (if a wrong
  format timestamp is passed). Handling both of them at the function
  level itself and just throwing out a pcacheexception. Seemed like the
  right way to do things

* Removing unwanted catch block

* BUGFIX: Adding missing sanitary check
Adding more tests

* This I think, concludes the list of tests that are *required* to
  proceed with the request layer. Would say, good to go.