This commit provides a method to predict the child occupancy bits of a
node based on the node's 26 neighbours.  The prediction is used to
contextualise coding of each occupancy bit.

This tool requires the use of the occupancyAtlas for neighbour lookup.
NB: a restriction in the current implementation requires that the
atlas size is at most 8³.

intra_pred_max_node_size_log2: 6

Bitwise geometry occupancy coding uses a mapping table to select entropy
contexts.  This commit employs a dynamic mapping which is updated after
each coding operation, replacing the previous static mapping tables.

NB: the proposed version used a context with a halving period
(max_count) of 64 symbols.  However, this conflicts with another
adoption (512 symbols), and a wholesale replacement of the arithmetic
codec and context model.  To resolve the conflict, the existing halving
period (128) is used.

Ohji Nakagami authored Jul 26, 2018 and David Flynn committed Oct 31, 2018

When trisoup was completely independent, trisoup handled lossless
geometry coding by using a leaf size of 1 and no triangles.  This
commit replaces that mode with the better performing octree geometry
coder.

This commit adds configuration data for new cat1 and cat3 sequences:

cat1, voxelised frames:
  boxer_viewdep_vox12
  longdress_viewdep_vox12
  loot_viewdep_vox12
  redandblack_viewdep_vox12
  soldier_viewdep_vox12
  thaidancer_viewdep_vox12

cat3, LiDaR sqeuences:
  qnxadas-junction-approach: 74 frames
  qnxadas-junction-exit:     74 frames
  qnxadas-motorway-join:     500 frames
  qnxadas-navigating-bends:  300 frames

Khaled Mammou authored Aug 27, 2018 and David Flynn committed Sep 03, 2018

Certain test sequences with 16-bit reflectance are actually 8-bit data that
has been scaled by 255.  This commit adds non-normative support to the
encoder and decoder to convert between the two representations through
the option "hack.reflectanceScale".

This commit disables the chroma sub-sampling in RAHT for the
common test conditions to permit better comparisons with the lifting
transform.

This configuration unifies the old configuration files and provides
greater test coverage.  Notable changes are:

 - configuration sets for octree vs trisoup, and pred/lift vs raht.

 - cat1 test sequences added to all test configurations

 - attribute quantization step sizes are aligned between all coding
   schemes.

 - levelOfDetailCount is unified where possible (cat3 = 10, mostly)

 - config dependent dist2 variation for a given sequence is removed

This commit allows the attribute codec to be parametrised by attribute
bitdepth.  The attribute bitdepth is signalled in the attribute's sequence
parameter set description.  The specified bitdepth affects cliping in the
attribute prediction and reconstruction process.

This commit updates the master configuration files to support:

 - new test conditions for cat3 tests
 - existing conditions for cat1 tests (for use by tmc13)
 - updates enc/decflags to use recommended forms
 - integrates pcerror flags (per condition / sequence)
 - adds sequence databases describing source files, and source
   parameters that may be used by other scripts.

The ctc-category-map.csv file has been removed -- a new version can be
provided if necessary.