Update context menu entries in project tree

[vkbo]

Summary:

This PR makes the following changes:

• The delete item menu entry for empty folders now correctly says "Delete Permanently" instead of "Move to Trash". Issue Empty folder context menu is inconsistent #1105.
• The menu entries for changing document layout now stays "Convert to" instead of "Change to". It is technically just a change of a setting, but to the user it makes more sense to say convert.
• The menu entries for status and importance now says "Set Status to ..." and "Set Importance to ..." instead of "Change [...] to" which is technically incorrect in the case where the user selects the same value as was previously set.

Related Issue(s):

Closes #1105

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