Add feature documentation for Offline User Replace and Supervisor CHW Create

[mrjones-plip]

tl;dr

We need to add high level feature documentation of two new-ish features to the Supervision section of the docs:

• Offline User Replace
• Supervisor CHW

Background

In 4.1 we shipped Offline User Replace and in 4.2 we plan on shipping Sup. CHW Create. Offline Replace is documented in reference docs and Sup. CHW Create will be documented in the same place when it goes live. These are both technical documentation for an app developer to use, but not high level feature documentation.

Approach

Using the docs linked in "Background" above as well as live demos posted to the forums for Offline User Replace and Supervisor CHW Create, we should add new content to the Supervision section of the docs.

[esthermmoturi]

Thanks @mrjones-plip I will work on this.

[mrjones-plip]

Linking original CHT Core tickets for sup. chw create and offline replace for cross referencing.