Remove original Show transform, rename Show2 to Show

Also, change the default waitKey value to be consistent with original
Show
Drop special casing of parallelism=0

Drop most special casing of parallelism=0, if parallelism=0 is received, set
the max number of threads to 1, and go through the same code as when more
threads are available.

Some outstanding issues, the following transforms are blocked out since they
aren't consistent with this change:
EditTransform
ElicitMetaDataTransform
StasmTransform

In stasm's case, a global mutex must be used, similarly ElicitMetaData reads
from stdin, and would also require a global lock. EditTransform can probably be
reimplemented through Qt similarly to Show
Simplify handling of parallelism

Default parallelism to IdealThreadCount+1, remove checks for input parallelism
> IdealThreadCount, since we find that a higher thread count can help in some
circumstances.

Don't use release/reserve thread to increase the size of the thread pool in
init, instead just set the max pool size directly.
Add comments on currently disabled transforms

Also, remove some extraneous curly braces.
Merge pull request #41 from biometrics/show_purge

Rename Show2 to Show, remove special casing of Parallelism=0 (not ready to merge yet)