Parce

- added XSLT language definition
- Xml now has tag_action() classmethod to return the action to use for a tag
name, this makes it easier to inherit Xml and add other actions to certain
tag names, like DocBook and XSLT do.
- when adding entries to registry, existing entries can be "inherited"
- added section and author fields to registry entry.
- documentation improvements

- small API changes in registry module. Removed some global functions, old
generic find() is now a method of Registry, and a fallback registry can be
specified.
- added DocumentInterface to more easily implement a (GUI text editor) document
helper/proxy with the parce Document API.
- added docio module, which adds save and load methods to Document using
language specific IO handling, mainly regarding encoding
- Document.modified is now a property; set_modified() has gone; the property
is in AbstractDocument now.

- added arabic and bagpipe pitch names to LilyPond words list
- added the default octave to all pitch names in the LilyPond words list
- added util.file_cache()
- added cache_none parameter to util.caching_dict()
- added the Document.url and encoding properties

- added AbstractDocument.find_block_by_number, block_count and
Block.block_number
- added tree.Range, together with Token.range() and Context.range()
- removed Context.tokens_range, context_trails, context_slices and slices
- removed Context.tokens_bw and util.tokens_bw, added reverse flag to tokens()
- Cursor and Block comparison methods are more robust now
- documentation improvements

- Cursor.selection() was added
- a new decorator is added to mark Transform methods so that they accept
untransformed contexts that would otherwise be silently ignored
- Worker: when an exception occurs during a tree build or transformation, the
state is set to idle, preventing hangs waiting for a condition.
- basic LilyPond indentation was added (not yet complete)
- an Ini transform was added
- documentation improvements

- added parce.Document.get_transform(), closes issue 4
- new work module, replacing BackgroundTreeBuilder and treedocument module
- util.Observable now uses a weak reference to methods.
- Cursor move and select methods now return self, so they can be chained
- added transform.Items.peek()
- Transform.find_transform() now uses a configurable naming scheme
- LaTeX parsing improvements
- added CSV language definition and transform