Docs: Model training documentation has no links on how to create database, load data etc.

[gaurav274]

1. Add links to create database command.
2. No explanation of TIME_LIMIT
3. Need a better explanation for PREDICT

[xzdandy]

The AI engine page is intended only to show the documentation for the AI engine. We will add a table to illustrate all configurable parameters.

For loading data, we will add a usecase documentation page to cover that.

[xzdandy]

Merge into #999