Fix/post angola

[rosannaamato]

Issue #137 suggests 17 fixes / improvements identified following delivery in Angola, this branch addresses 9 of them (listed below). Comments added to #137 describe which commits address specific improvements.

• Inconsistent location for location of data (historical in WS3 but not WS2)
• 4.2c solution is for pr not tm and also only historical not future as well
• Wet days - using threshold of 0 not 1 -replace custom aggregator with count > 1
• Future dir should be explicitly rcp85
• Mean over season should be over time (this should remove redundant time dimension)
• Inconsistent on use of REMO2015 in filenames
• Needs to be made VERY clear when we expect something will fail (worksheet 1 - merge problem)
• Remove f strings and remaining .format (just use concatenation)
• set domain name as variable at start.

Changes are applied to EAS-22 worksheets 1-6 + solutions, testing was undertaken using data in /project/ciid/projects/PRECIS/worksheets/data_v2/EAS-22.

Please review changes.

[nhsavage]

apart from the addition of the files in .idea (which I have taken out of the branch) these changes seem great to me. Thanks for your efforts.