Add documentation explaining differences between consumer and democ consumer

[shaspitz]

Problem

There is not much written documentation (or code comments) explaining the difference between a consumer and democracy consumer. We should answer the following questions:

• Why does the democracy consumer app have a staking keeper? AFAIK for a normal consumer, the consumer CCV keeper acts as the staking keeper
• Why do we maintain apps for both a normal consumer and democracy consumer? This is not intuitive from reading code

Closing criteria

Add a markdown explaining the relevant differences in implementation and functional behavior. Sufficient code comments could also suffice.