Update Caesar documentation

[ramanakumars]

Update the Caesar technical documentation (zooniverse.github.io) with more details on the individual components.

• Caesar overview
  • Overview of different pages (workflows/projects)
  • Adding new project or workflow to Caesar
• Extract
  • Creating an extractor
  • Overview of different extractors
    • Blank extractor
    • Question extractor
    • Pluck field extractor
    • Survey extractor
    • Shape extractor
    • External extractor
• Reducers
  • Creating a reducer
  • Reducer configuration keys
  • Overview of different reducers
    • Consensus
    • Count
    • Simple Stats
    • First Extract
    • SQS
    • Rectangle
    • External
• Rules
  • Subject vs User Rules
  • Creating Rules
  • Rule Syntax
  • Creating Rule Effects
• Data Requests