Feature: Reorder Depcode functions and make appropriate functions private

[yardasol]

Background and motivation

As raised in #172, and #174, the abc.py filename is confusing.

Additionally, there are many functions in the Depcode child classes that have functions that should be private but are not. This can be confusing when reading web-hosted documentation.

Additionally, the functions in the Depcode classes need to be reordered to fit the first-executed first-in-code format.

Description of idea

Do the above after all Depcode work is done.

Implementation details

See above.

Potential snags

None