Gaffer v1.20 released

[n3101]

There are no big items this month.

#2519 fixes a niche bug affecting the MapStore when using the GetElements operation.

gchq/gaffer-tools#944 adds a graphIds helper to the gafferpy python API. This is a limited fix for the short term. For the longer term we will be developing the alternative “fishbowl” dynamic python API to replace gafferpy and will develop a more elaborate solution. In the meantime, see the original issue gchq/gaffer-tools#704 for the discussion around this fix.

In Gaffer v1.19 #2211 added a few functions. Now, gchq/gaffer-tools#941 makes these available to gafferpy; and gchq/gaffer-doc#235 adds some example doc.

In Gaffer v1.19 #2476 added some refinements to access control of NamedOperations. Now, gchq/gaffer-doc#232 adds some documentation for these changes.

The remaining changes in this release are housekeeping fixes.