Share source setup. #3996.

Moving the source data setup to one-time-called `before(:all)` blocks
reduces the time for the entire spec on my machine from 17m to 8m.

Since this is testing cloning a deep tree, it makes some sense that
setup and execution would take the same amount of time. So perhaps
sharing the actual cloned object between examples would speed things
up also.
Use `before(:all)` init for subject in bulk of specs. #3996.

The slowest part of this suite before this commit was iterating over
all the various associations and verifying if they were cloned (or
not). This was slow because the clone itself is slow. But since the
test data doesn't change for this subset of the specs, the clone can
safely be computed once (in `before(:all)`) and then each association
examined in a separate spec.

On my laptop, this commit provides a 33x speedup for the full
case_cloner_spec (10 minutes down to to 18 seconds).
Merge pull request #207 from NUBIC/3996-cloner_speed

Improve speed of CaseCloner specs (#3996)