Update documentation

[flawmop]

Belated issue to accommodate #63

Some outstanding areas to cover :

• https://ap-nimbus.readthedocs.io/en/latest/developer/command-line/index.html#invoking-ap-nimbus-client-direct-as-a-cli
• Building the minified js in https://github.com/CardiacModelling/ap-nimbus-client
• Add to the "Updating ApPredict" (https://ap-nimbus.readthedocs.io/en/latest/developer/updating-appredict/index.html) section.

[flawmop]

"Updating ApPredict" and "Building the minified js" are being included in docs-appredict branch

[flawmop]

Added Gary as an assignee as he'll be involved in verifying the "Updating ApPredict"