JDK8, lint fixing (#2888)

* Use Kotlin JDK8

* Satisfy a ton of lints

* Run res/layout files (and manifest) through reformatter

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

@@ -101,8 +101,8 @@ class SettingsDownloadController : SettingsController() {
                         .subscribeUntilDestroy { isVisible = it }
 
                 preferences.downloadNewCategories().asObservable()
-                        .subscribeUntilDestroy {
-                            val selectedCategories = it
+                        .subscribeUntilDestroy { mutableSet ->
+                            val selectedCategories = mutableSet
                                     .mapNotNull { id -> categories.find { it.id == id.toInt() } }
                                     .sortedBy { it.order }
 

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

@@ -118,8 +118,8 @@ class SettingsLibraryController : SettingsController() {
                 entries = categories.map { it.name }.toTypedArray()
                 entryValues = categories.map { it.id.toString() }.toTypedArray()
                 preferences.libraryUpdateCategories().asObservable()
-                        .subscribeUntilDestroy {
-                            val selectedCategories = it
+                        .subscribeUntilDestroy { mutableSet ->
+                            val selectedCategories = mutableSet
                                     .mapNotNull { id -> categories.find { it.id == id.toInt() } }
                                     .sortedBy { it.order }