Style views and category-list

[TrimmingFool]

Hi, there are some new components which need theming:

v4.2 includes a new Views panel: https://github.com/Novik/ruTorrent/pull/2535

v4.3 includes a rewritten category-list with web-components (making styles for v4.2 and v4.3 incompatible): https://github.com/Novik/ruTorrent/pull/2588

Additionally, I added a hover indication for input.Button and button.