Rework presentation of search results

[wutschel]

Description

Closes #733.

This PR reworks the presentation of search results and delivers two main improvements and a small one.

1. The search result list in Global Search does now show the section headers with the item type, e.g. movie or artists. This way it easy to recognize what type of item is shown in the list.
2. All search results are now sorted by ascending label (for Global Search by "Type" within a section). This improves the user experience where Kodi does not provide sorted lists or the lists are sorted by something else, e.g. playcount for the "Top 100 Songs".
3. Support searching the "year" key in the data, which allows to search for release years of movies, TV Shows, music videos, albums, and songs.

Screenshots (in each pair: left = old, right = new):

Summary for release notes

Improvement: Show sections with item type for search results in Global Search
Improvement: Sort search results by ascending label
Improvement: Scroll back to top when search ended
Feature: Support searching year via the search field