Adapt MERIS processor for the 4th reprocessing

[marpet]

MERIS processor should be able to use the data from the 4th reprocessing.

This is actually a general requirement for the S3TBX and multiple processors. Due to the Lakes CCI project this is the first specific request.
The general usage shall be considered when implementing this.

Possible approach:
Create an adapter Product class which maps the names and data from 3rd to 4th reprocessing and adopt the processor to the 4th reprocessing data structure. The other way around is also possible, mapping from 4th to 3rd reprocessing. This would mean less work in adapting the processors, but we should go on with the new format and do not stick to the old 3rd reprocessing format.

[marpet]

The MERIS Idepix operator will use this automatically when detecting a 4th reprocessing product.
SNAP 9 will have an AdaptorOperator to adapt 4th reprocessing products to operators which expect 3rd reprocessing products as input.
The AdaptorOperator is included in the idepix-meris module for the SNAP/Idepix 8 branch.