Mutwo-core

Changed
- refactor mutwo code: split mutwo into `core` and `ext` packages. `core` only contains the main / shared / most important code

Changed
- refactor complete code base: rename all plural variables from `objects` to `object_containertype` (for instance `pitches` to `pitch_list`) for clearer code

Deprecated
- `time_brackets` module (in events and in converters): neither well tested nor documented, therefore removed or exported soon (and should only be added again if it is more stable)
- `absolute_times` property (replaced by `offset_tuple` property)

Fixed
- `IsisConverter`: fix missing argument for `convert` method

Added
- `GraceNotesConverter` in `converters.symmetrical.grace_notes`
- `bend_after` playing_indicator and abjad attachment
- `duration_line_dashed` and `duration_line_triller` playing indicators and abjad attachments
- `ArticulationConverter` in `converters.symmetrical.playing_indicators`
- `StacattoConverter` in `converters.symmetrical.playing_indicators`
- `Trill` in `playing_indicators` and in `abjad.attachments`
- `TrillConverter` in `converters.symmetrical.playing_indicators`
- 'col legno tratto' (c.l.t.) to playing indicator and abjad attachment `StringContactPoint`
- `call_function_except_attribute_error` in `tools` module

Changed
- move typing literals from `parameters.playing_indicators` to `parameters.playing_indicators_constants`
- renamed function in `utility.tools` module `class_name_to_object_name` to `camel_case_to_snake_case`

Changed
- `range_at` property of `Tendency` class in `koenig` module returns `Range` object

Removed
- abstract base class `Parameter`

Added
- syntactic sugar for setting playing indicators:
- `note_like.playing_indicator_collection.tie = True` is now the same as `note_like.playing_indicator_collection.tie.is_active = True`
- literal type hints for playing indicators

Added
- `brun` module in `generators` with function `make_bruns_euclidean_algorithm_generator`
- function `make_wilsons_brun_euclidean_algorithm_generator` in `wilson` module

Changed
- rename `pitch_or_pitches` property of `NoteLike` to `pitch_list`
- rename `playing_indicators` property of `NoteLike` to `playing_indicator_collection`
- rename `notation_indicators` property of `NoteLike` to `notation_indicator_collection`
- rename `grace_notes` property of `NoteLike` to `grace_note_sequential_event`
- rename `after_grace_notes` property of `NoteLike` to `after_grace_note_sequential_event`