Writing docs

[paolap]

I've started adding readthedoc structure.
Plan is to cover:

Setup, this is necessary if using new model configuration, for some users it might just mean knowing they might have to check mappings for others might mean
To understand tool structure:

• CMOR requirements
  "Tutorials":

• creating mapping via cli_db

• creating new CMOR table via cli-db

• adding cmor var via cli_db

• setting new CV

• using existing setting

• modifying existing mapping

• adding calculation to mapping/code

How to actually run tool

• running mopper
• checking logs
• where is output
• ...