Bins helpers and ability to update clips in a dedicated bin

Description

Some helpers were added to create and retrieve bins.
For example, importing media in a dedicated bin can be done with:

# Get the current Premiere project
project = engine.current_project
# Make sure needed bins exist
my_bin = project.ensure_bins_for_path("/path/to/my/import/bin")
# Create a new clip for some media in the bin
clip = my_bin.create_clip_from_media("/path/to/my/media/on/disk/media.mov")
# Adjust the clip name if needed
clip.name = "Demo media"

A new import_in_bin_template setting is now retrieved by the default scene operation hook: if set to a template name defined in core/templates.yml, clips are not updated in place, but new clips with updated media are created in a bin matching the resolved path.

For example:

• In core/templates.yml: premiere_import_bin: 'Published/{YYYY_MM_DD}
• In breakdown2 app settings: import_in_bin_template: premiere_import_bin

What's Changed

• 12123 import as new clips by @gplsteph in #6

Full Changelog: v1.2.2...v1.2.3