Param

Minor release for Panel-related bugfixes and minor features, from philippjfr.

- Fix serialization of Tuple, for use in Panel (446)
- Declare asynchronous executor for Panel to use (449)
- Switch to GitHub Actions (450)

- Fixed ClassSelector.get_range when a tuple of types is supplied (360)

- Compatibility with Python 3.8
- Add eager option to watch calls (351)
- Add Calendar and CalendarDateRange for real date types (348)

Enhancements:

- Allow param.depends to annotate functions (334)
- Add context managers to manage events and edit constant parameters

Bug fixes:

- Ensure that Select constructor does not rely on truthiness (337)
- Ensure that param.depends allows mixed Parameter types (338)
- Date and DateRange now allow dt.date type (341)
- Ensure events aren't dropped in batched mode (343)

Full release with new functionality and some fixes. New features:

- Added support for instance parameters, allowing parameter metadata to be modified per instance and allowing parameter objects to be passed to Panel objects (306)
- Added label slot to Parameter, to allow overriding attribute name for display (319)
- Added step slot to Parameter, e.g. to control Panel widget step size (326)
- Added keywords_to_params utility for deducing Parameter types and ranges automatically (317)
- Added support for multiple outputs from a Parameterized (312)
- Added Selector as a more user-friendly version of ObjectSelector, accepting a list of options as a positional argument (316)

Changes affecting backwards compatibility:

- Changed from root logger to a param-specific logger; no change to API but will change format of error and warning messages (330)
- Old abstract class Selector renamed to SelectorBase; should be no change unless user code added custom classes inherited from Selector without providing a constructor (316)

Bugfixes and other improvements:

- Various bugfixes (320, 323, 327, 329)
- Other improvements (315, 325)

For more details, you can see a [full list of changes since the previous release](https://github.com/ioam/param/compare/v1.8.2...v1.9.0).