Reynir

Various grammar fixes. The pronoun 'sá' (_ábendingarfornafn_) was not being handled correctly in possessive case ('þess'). Prepositional phrases were not allowed in some cases where they should have been allowed.

More accurate handling of compound words, allowing only grammatically valid prefixes and suffixes. Fixed bugs in augmented terminal variants (``SimpleTree.flat_with_all_variants`` property).

Terminals in parse trees are now more detailed and accurate. They are augmented with information collected from BÍN, and split more accurately into atomic terminals in the case of composite tokens such as dates, timestamps and amounts. As an example, *3 milljarðar danskra króna*, which is seen and parsed as a single amount token, is now split into four terminals when returned by the property ``SimpleTree.flat_with_all_variants``.

Added the `_Sentence.ifd_tags` property to obtain a list of Icelandic Frequency Dictionary (IFD) tags for a sentence.

Enhanced the `SimpleTree.nominative_np`, `.indefinite_np` and `.canonical_np` properties.

Support for new token types: ``TOK.DATEABS``, ``TOK.DATEREL``, ``TOK.TIMESTAMPABS``, ``TOK.TIMESTAMPREL``, ``TOK.MEASUREMENT``. Extended grammar support for date and time phrases. Added ``SimpleTree.top_matches(pattern)``, and the tree properties ``nominative``, ``indefinite``, ``canonical``, ``nominative_np``, ``indefinite_np``, and ``canonical_np``. Documentation and test suite updates.

This release adds the `SimpleTree.all_variants` property. Python-side parse tree construction from the C++ tree is now faster since empty nodes are now immediately translated to `None`.