Improvements functionality of various dialogs

[vkbo]

Summary:

This PR fixes a bunch of minor details on the Welcome dialog:

• The opacity of the highlight colour for a selected item has been reduced.
• When a project is removed from the list, the first item is selected automatically.
• When a project is requested opened, the dialog hides before the open project signal is emitted, so that it looks like the welcome dialog closes before the project is opened. In reality, it closes after the signal. Previously, when it stayed visible, any dialogs that popped up during the closing of the previous project and opening of the next would open on top of the welcome dialog, which was a bit confusing.
• Adds a modified version of QComboBox, QSpinBox, and QDoubleSpinBox where the mouse scroll wheel is only captured by the widget when the widget has focus. This prevents accidentally changing the value when scrolling the page. The new widgets are used on the Welcome dialog New project form, and also replaced in Preferences, Project Setting and Manuscript Build Settings.

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