port TEncEntropy and TEncSbac into internal Entropy and SBac classes

The Entropy class will be short-lived
entropy: remove all data members except m_entropyCoder

The three variables were only used to maintain state through recursive calls
to encodeTransform() and could be just as easily kept on the stack.

The class is now a pure reflector to the SBac class and can be merge into it
piece-wise.
entropy: hoist all non-trivial Entropy methods into SBac

Now Entropy only exists in entropy.h, making further cleanups possible
entropy: fix msvc warnings about signed/unsigned operations
entropy: remove default argument to encodeIntraDirModeLuma()
entropy: reorder SBac methods for more clarity
entropy: remove unnecessary API differences between Entropy and SBac

These would only trip us up as we try to remove Entropy entirely
remove m_entropyCoder from FrameFilter and SAO code

Lo and Behold! the SAO code suddenly makes a tad more sense when this useless
redirection is removed
sao: remove redundant braces and other nits
frameencoder: do not use Entropy object to code stream headers
entropy: remove m_slice member from SBac class

The slice object was only needed in resetEntropy() and determineCabacInitIdx()
and could be passed to those two methods easily.

It was also being used in two functions to gain access to the scaling list, but
this was actually a problem for us because headers can be queuried before any
slice objects are initialized so it was better to pass in the scaling lists
directly from the top Encoder. Note this fixes a bug in scaling list support -
we were previously incapable of signaling them properly in our stream headers.

Removing this member variable lets us clean up a lot of redundant setSlice()
calls and other cruft
frameencoder: do not pass member variable to its own function

We were still passing an array of Bitstream objects to encodeSlice() even though
the array was made a member of the class so it was available via m_outStreams.
Within the function is was using both pointers, unhelfpully.
frameencoder: remove most traces of the Encoder class
remove Entropy from TEncCu, TEncSearch, and CTURow

Instead, give each an SBac pointer that they are supposed to use to code the
bitstream.
entropy: remove now unused Entropy class
entropy: make m_cabac member of SBac class a non-pointer instance

This forces a 1::1 correspondence between SBac and CABAC instances, which cleans
up a mess of confusing allocations and assignments.

This moves the CABAC class into entropy.h and it is no longer referenced outside
of this header and entropy.cpp, allowing us to further combine them.
framefilter: rename m_rdGoOnSbacCoder to m_sbacCoder - there is only one
entropy: allocate RDO coders as dual-dimensioned array

In order to make this change even less intrusive as it was going to be, I
simultaneously changed the load/store functions to take references instead of
pointers (since NULL pointers are not supported).

This further simplified setup/tear-down code and should improve data locality
ctu: rename m_sbacCoder to m_rowEntropyCoder
frameencoder: remove barely use helper function getRDGoOnSbacCoder