Rename boolean properties

[essvee]

Properties with a boolean dataype need to be renamed after the form 'isName', ref #396. This relates to the following properties:

CollectionDescriptionScheme.distinctObjects ObjectGroup.currentCollection
ObjectGroup.knownToContainTypes
RecordLevel.derivedCollection
SchemeMeasurementOrFact.mandatoryMetric
SchemeMeasurementOrFact.repeatableMetric
SchemeTerm.mandatoryTerm
SchemeTerm.repeatableTerm

The name will need changing in...

• ltc_standard_terms_draft.csv (https://github.com/tdwg/cd/blob/review/standard/terms/ltc_standard_terms_draft.csv)
• ltc_skos_mapping.csv (https://github.com/tdwg/cd/blob/review/standard/terms/ltc_skos_mapping.csv)
• ltc_datatypes.csv (https://github.com/tdwg/cd/blob/review/standard/terms/ltc_datatypes.csv)
• json schema defs for the relevant terms (https://github.com/tdwg/cd/tree/review/standard/json-schema)
• json examples, wherever present (https://github.com/tdwg/cd/tree/review/examples/class-level%20json%20examples)

[essvee]

Closed by #426

[essvee]

Wiki Section 2.2. 'Collection Description Schemes' text updated to match in revision c68dd85