Misc. GUI Changes

[caseif]

Small changes I'd like to make the GUI before release:

Easy

• [x] Fix database GUI reloading every time a new song is played
• [x] Hide cursor with GUI
• [x] Update progress slider more frequently if possible
• [x] Switch cursor to pointer when hovering control buttons
• [x] Remove "Flip BG" button (hotkey for it is fine, also need to discuss this further with Incept) (now bound to 'F' key)
• [x] Add button to open database GUI
• [x] Disable "Add to Database" button when no song is selected
• [x] Fix play/pause button not updating when new song is selected
• [x] Add confirmation dialog to "Delete Database" button

Medium

• [x] Add "X" button to database GUI
• [x] Allow database items to be edited
• [x] Dynamically update song artist/title based on text fields
• [ ] Maybe switch cursor to progress or busy when loading images/database
• [x] Add shuffle/repeat buttons to controls

Hard

• [x] Paginate database GUI
• [x] Make progress & volume sliders draggable

Of course I'd appreciate feedback from @itsIncept on some or all of these.