Mid.CBF scan configuration for correlation (JSON script)

Review the DDD and ICD  to refine the set of parameters for scan configuration for correlation. Define the JSON schema. Implement command 'configure scan' for correlation and the related attributes.

Interface is described in SKA1 CSP LMC to CSP Sub-elements Interface Control Document, SKA-TEL-CSP-0000019, 2018-10-25. 

Publish JSON schema for scan configuration on 

https://confluence.skatelescope.org/display/SE/CSP_Mid+Scan+Configuration+for+Correlation

Functionality:

Mid.CBF accepts and responds to command configure scan (imaging), obsState transition as expected. 

Implement command that parses received JSON script, sets the attributes, and forwards configuration to VCCs and FSPs as required. This version of Mid.CBF software implements TANGO Devices VCC (Very Coarse Channalizer) and FSP (Frequency Slice Processor), but does not include software running on the TALON-DX Boards (in the embedded processor). In fact, the TANGO Devices VCC and FSP implement only rudimentary functionality required to receive configuration from Mid.CBF Subarray and to respond. VCCs and FSPs implement attributes set by command 'configureScan', which represent a subset of the attributes that will be implemented in the full version.

Mid.CBF should be able to detect errors and reject invalid command. When an error is detected, an exception is raised, and the sub-array configuration remains as-is. 

Note: All Mid.CBF software implemented by this feature is part of Mid.CBF Master Control Software (MCS), when deployed Mid.CBF MCS will run on a server. This feature does not include Mid.CBF software running on TALON-DX boards (embedded software).