Update PyOTA for comnet

[lzpap]

Description

comnet is the community run test network of IOTA.
Update documentation with details about comnet. (Required MWM = 10)
Maybe add comnet configuration option to API classes.

Motivation

Provide more info about comnet to users.

Requirements

Write a list of what you want this feature to do.

1. Explicitly state MWM=10 for comnet in documentation
2. Add comnet option to API class (refactor the current devnet option to be more generic)

Are you planning to do it yourself in a pull request?

Maybe.