Corrected compiler warnings and removed unnecessary JavaDoc
MODE-1956 Add helper function to (un)escape illegal JCR characters
MODE-1958 DDL Sequencer should use Jsr283Encoder rather than its own custom code
Added a getter in Session to return a class of utilities. Removed the code from DDL sequencer framework dealing with converting JCR-illegal characters
and replaced with calls to the new utilities class.
MODE-1956 MODE-1958 Simplified how the encoding/decoding methods are exposed

Removed the separate 'JcrUtils' interface from the public API (along with
the implementation), and moved the 'encode' and 'decode' methods to the
ModeShape-specific 'Session' interface.