Imported implementation for updating library by next expected update from Neko (#5436)

* Imported implementation for updating library by next expected update from Neko. This sort uses the last 4 updates for a manga to compute an average time between updates and then extrapolates when the next update should occur.

Currently seems to work perfectly. However, I may have silently messed something up along the way.

All code and algorithms are credited to kyjibo on GitHub. The original commit adding this functionality is here: 681003926a

* Imported implementation for updating library by next expected update from Neko. This sort uses the last 4 updates for a manga to compute an average time between updates and then extrapolates when the next update should occur.

Currently seems to work perfectly. However, I may have silently messed something up along the way.

All code and algorithms are credited to kyjibo on GitHub. The original commit adding this functionality is here: 681003926a

* Remove commented-out line from LibraryUpdateRanker

I missed removing this when first committing. The removed line is a holdover from Neko, which requires 7+, but I removed the function that requires this.

app/src/main/res/values/strings.xml

@@ -40,6 +40,7 @@
     <string name="action_sort_total">Total chapters</string>
     <string name="action_sort_last_read">Last read</string>
     <string name="action_sort_last_checked">Last checked</string>
+    <string name="action_sort_next_updated">Next expected update</string>
     <string name="action_sort_latest_chapter">Latest chapter</string>
     <string name="action_sort_chapter_fetch_date">Date fetched</string>
     <string name="action_sort_date_added">Date added</string>