Merge new features from PocketSphinx 5 (and simplify things)

[dhdaines]

Pull in a ton of changes from PocketSphinx 5.0.0:

• WebRTC VAD and Endpointer based on it (Javascript API is not fully mature here)
• Direct get/set CMN API instead of hacking the config
• Eliminate overflows in GMM computation
• Compile JSGF to correct (but wasteful) FSGs
• Interact with configuration and results using JSON (exclusively, in JavaScript)
• Subword alignments

Then do ... some other things:

• Eliminate "pocketsphinx" names from the API and drop any pretense at backward-compatibility
• Replace superfluous Cython classes with namedtuples
• Consistenly report start and duration in Python and JavaScript segmentations (C will follow)
• Remove FSG model and Config classes from JavaScript API, making code more compact and eliminating memory leaks
• Grow feature buffers by default to make two-pass alignment work as expected

[joanise]

Wow, yeah, this is a huge PR. I wouldn't be able to give you much useful feedback if I tried... Thanks for making this update!