UI updates

[danomatika]

This PR is some general UI updates to piggy-back off of PR #4. I wanted to separate them so it would be easier to tell what changed.

Main updates concern making the current repo UI more closely match that of the 1.0.3 release as well as a few modernization and layout tweaks:

• changed main window layout slightly to match 1.0.3 release
• Notes tab is selected on open
• table add/remove button are replaced by more modern +/- segmented controls
• window and endpoint panels slightly slimmed
• removed unused plus icon file

Here are some screenshots:

1.0.3 release version

UI updates: window

UI updates: endpoint panel