icat.lucene support for InvestigationSample

[patrick-austin]

Supports the new InvestigationSample entity and the removal of the direct Investigation<->Sample relationship for icat.lucene. Note this is dependent on icatproject/icat.lucene#75 and icatproject-contrib/icat-ansible#123

• Change ansible branch to one which (will) install the latest version of lucene, required for the InvestigationSample to be indexed in place of Sample.
• Re-introduces the Investigation->Sample mapping when indexing documents with the additional step of InvestigationSample
• Remove "sample.investigation.id" field, as it is no longer relevant/required (Investigation id does not directly appear on Sample anymore).
• Replace references to the Sample index with InvestigationSample.
• Add special case to handle the pluralisation of Investigation.samples (rather than Investigation.investigationSamples) when faceting
• Re-enable previously failing tests.