Update the Outline View panel

[vkbo]

Summary:

Various updates to the "Outline" panel following PR #1057, and implementing #1041 for the Outline.

The following changes were made:

• Add a top level widget that contains the entire Outline View.
• Move the details panel code to the outline.py file.
• Add a toolbar to the top of the Outline view with a dropdown box to select which Novel folder to view.
• Add a refresh button to the tool bar.
• Move the context menu for changing columns to a menu button on the tool bar.
• Remove the Rebuild Outline and Auto-Update Outline options from the main menu.

Related Issue(s):

Resolves part of #1041

Reviewer's Checklist:

• The header of all files contain a reference to the repository license
• The overall test coverage is increased or remains the same as before
• All tests are passing
• All flake8 checks are passing and the style guide is followed
• Documentation (as docstrings) is complete and understandable
• Only files that have been actively changed are committed