[Typo3-doc] move Mysteries of cHash to doc matrix

[Mark Ravitz]

The ' mysteries of &cHash' document contains absolutely
vital information about caching in general as well as cHash.
It ought to be moved to the Documentation Matrix and renamed
to something like Caching and cHash.

After reading it I realized that I have wasted a many many hours
because I didn't have that table at the end of document
which lists exactly what determines whether a page will
be cached.

Mark Ravitz