A python script is provided to accumulate stats from counts.stt
files generated from multiple encoding examples. Command line:
python ../../tools/aggregate_entropy_stats.py [dir of stats files]
 [keyword of filenames] [filename of final stats]

Plus cosmetics on output format of optimized prob tables. The comma
after the last element of each dimension is removed, i.e.,
before: {
          { 128, 128, 128, },
          { 128, 128, 128, },
        }
after:  {
          { 128, 128, 128 },
          { 128, 128, 128 }
        }.
The reason is to avoid moving '}' to a second line after applying
clang-format.

Change-Id: I3b764f4c89b7aefbaf48ac00b8c83713caf75a5d