tinyTiM 1.5.0 alpha 2 released

Second alpha version of the tinyTiM 1.5.0 branch

Changes:
Features:
- ``voc`` package added which provides access to common PSIs.
- ``DuplicateRemovalUtils`` added. Used to remove
duplicate Topic Maps constructs from topic maps, topics,
associations, and names
- ``TypeInstanceConverter`` added. Used to convert
type-instance associations into the topic's [types]
property.
- ``tmapi.TopicNamesIndex``, ``tmapi.OccurrenceIndex``
and ``tmapi.VarinatsIndex`` use an optimized reindex
algorithm.
- Property to let ``Variant`` instances return the union
of their 'own' scope and the parent's scope.

Bugfixes:
- ``DatatypeAwareConstruct`` sent wrong event. Fixed
- All indexes return copies of their collections to avoid
concurrent modification exceptions.