Theme rework & stylesheets #133
Description
The current implementation of themes all around are a bother and do not help in any major way, furthermore there are theme conflicts when you wish to use a stylesheet, meaning that it could potentially bring some things to not work proper, an issue.
A complete rework for themes would probably be of use, as well as re-implementing custom UI elements hierarchy to not cause possible crashes due to some issues (recursion issue) as mentioned in #102
Reworking the theme structure would help immensely and alleviate potential risks where more file formats are introduced.
Finally, reworking the UI itself to make actual use of some of its features would go an extremely long way for mod customization.