Update ranking (#1772)

* Add LibraryUpdateRanker

This class provides various functions to generate Comparators that can 
be used to order the manga to update.

One such ordering is by relevance:
It prioritises manga that were updated more recently.

Another Ordering is by lexicographic order:
This is the default behaviour.

* Use relevanceRanking scheme

Instead of default(noRanking/lex ranking) now mangaList is sorted with 
relevanceRanking.

* Add UI and associated variables & strings for Update Ranking.

* Use user preferences to determine update ranking scheme.

* Refactor relevanceRanking to latestFirstranking.

This name seems to better reflect the ranking scheme and frees up the 
name relevanceRanking for future use.

* Set latestFirst scheme as default.

(Changing over from lexicographic scheme)

* Fix 1

[Convert LibraryUpdateRanker to a object.](./files/82f263749f0ae775385b23dd919f1865360db969#r287513539)

[Nitpick: Add lines](./files/82f263749f0ae775385b23dd919f1865360db969#r287540256)

[Replace Java comparator](./files/82f263749f0ae775385b23dd919f1865360db969#r287539976)

[Nitpick: Add local variable](./files/82f263749f0ae775385b23dd919f1865360db969#r287514805)

* Fix 2

[Weird import](./files/82f263749f0ae775385b23dd919f1865360db969#r287513709)

[Default value](./files/82f263749f0ae775385b23dd919f1865360db969#r287540064)

[Use existing Strings](./files/82f263749f0ae775385b23dd919f1865360db969#r287514476)

[Use Library update order](./files/82f263749f0ae775385b23dd919f1865360db969#r287540204)

app/src/main/java/eu/kanade/tachiyomi/ui/setting/SettingsGeneralController.kt

@@ -159,6 +159,22 @@ class SettingsGeneralController : SettingsController() {
                             selectedCategories.joinToString { it.name }
                     }
         }
+        intListPreference{
+            key = Keys.libraryUpdatePrioritization
+            titleRes = R.string.pref_library_update_prioritization
+            // The following arrays are to be lined up with the list rankingScheme in:
+            // ../../data/library/LibraryUpdateRanker.kt
+            entriesRes = arrayOf(
+                    R.string.action_sort_alpha,
+                    R.string.action_sort_last_updated
+            )
+            entryValues = arrayOf(
+                    "0",
+                    "1"
+            )
+            defaultValue = "1"
+            summaryRes = R.string.pref_library_update_prioritization_summary
+        }
         intListPreference {
             key = Keys.defaultCategory
             titleRes = R.string.default_category