Update annotations and add deleteLater to several temporary objects

[vkbo]

Summary:

This PR cleans up some annotations here and there, and adds the deleteLater call to a number of objects. In particular, the editor context menu needs this as each instance of the menu seems to remain in memory. All dialogs and tools have been redesigned to clean up after themselves where possible.

To test the memory cleanup, a new flag --meminfo has been added to the command line that will display momory information on the status bar when set.

Related Issue(s):

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