Refactor ButtonLayout module components

- Rename ButtonLayout module to just Buttons

- Rename ButtonLayout into AutoDirectionLayout and move it to Base,
  it's useful not just for buttons

- Rename OtherButton into GroupButton, which is now the base of all
  other Buttons buttons

- Add generic (Positive|Middle|Negative)Button components, which are now
  the base for (Apply|Cancel)Button

src/gui/Pages/Chat/RoomPane/SettingsView.qml

@@ -4,7 +4,7 @@ import QtQuick 2.12
 import QtQuick.Controls 2.12
 import QtQuick.Layouts 1.12
 import "../../../Base"
-import "../../../Base/ButtonLayout"
+import "../../../Base/Buttons"
 
 HFlickableColumnPage {
     id: settingsView
@@ -63,7 +63,7 @@ HFlickableColumnPage {
         color: theme.chat.roomPane.roomSettings.background
     }
 
-    footer: ButtonLayout {
+    footer: AutoDirectionLayout {
         ApplyButton {
             enabled: anyChange
             loading: saveFuture !== null