Remove usages of die() from the API cache

Review Request #7298 — Created May 13, 2015 and submitted — Latest diff uploaded

Information

RBTools
release-0.7.x
f881b5f...

Reviewers

All usages of die in the HTTP cache for the API have now been
replaced to raise a new exception, CacheError, instead.

The --cache-location flag is now accepted by clearcache and the
--disable-cache flag (which was added by mistake) was removed.

Ran unit tests.