add ktlint plugin to project and apply default code style (#2209)

* add ktlint plugin to project and apply default code style

* some manual adjustments, fix wildcard imports

* update CONTRIBUTING.md

* fix formatting

app/src/main/java/com/keylesspalace/tusky/interfaces/AccountSelectionListener.kt

@@ -19,4 +19,4 @@ import com.keylesspalace.tusky.db.AccountEntity
 
 interface AccountSelectionListener {
     fun onAccountSelected(account: AccountEntity)
-}
+}

app/src/main/java/com/keylesspalace/tusky/interfaces/RefreshableFragment.kt

@@ -8,4 +8,4 @@ interface RefreshableFragment {
      * Call this method to refresh fragment content
      */
     fun refreshContent()
-}
+}

app/src/main/java/com/keylesspalace/tusky/interfaces/ReselectableFragment.kt

@@ -8,4 +8,4 @@ interface ReselectableFragment {
      * Call this method when tab reselected
      */
     fun onReselect()
-}
+}