Add details to inference and serialization documentation

[meissnereric]

*Issue #99 , #122, #84 *

Description of changes:
Add a more detailed description of the inference process and machinery.
Add documentation on how serialization works.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-io]

Codecov Report

Merging #144 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #144   +/-   ##
========================================
  Coverage    85.06%   85.06%           
========================================
  Files           78       78           
  Lines         3898     3898           
  Branches       660      660           
========================================
  Hits          3316     3316           
  Misses         383      383           
  Partials       199      199

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e29ea53...49b6d4e. Read the comment docs.

[zhenwendai]

• We need to make a tutorial notebook to give an example of saving and loading of inference results.
• Some of the texts need to be updated, once the zipping work is done for serialization.