Areaimol task

[stuartjamesmcnicholas]

As requested in https://github.com/ccp4/ccp4i2-issues/issues/111 an Areaimol task.

This task offers:

• basic DIFFMODE OFF functionality to calculate SAS and produce output file with either atom, residue averaged or GXGRATIO "normalised" areas in "B-factor" column.
• DIFFMODE IMOL to calculate surface of intermoleculat contacts using a symmetry translation in each direction. Output can be by atom or residue averaged.
• DIFFMODE COMPARE to compare the surface area of 2 models. The residue numbers must be matched in order for this to work. Output can be by atom or residue averaged.
• EXCLUDE keyword for space separated list of residue types to exclude from calculation.

NB. DIFFMODE WATERS is not supported because it does not appear to work. The WATER example in $CCP4/examples/unix/runnable/areaimol.exam crashes when running from command line.

[stuartjamesmcnicholas]

I have reverted to draft. I have decided the report should be prettier.

[stuartjamesmcnicholas]

I see no easy way to override the font-family of a pre without altering CCP4ReportParser.py or xreport.css. pre is probably the correct way to display the space formatted log file text. So I am minded to leave things as is and declare this ready for review.