Split ApplySelection into CompleteOrPrevSelection and CompleteOrNextSelection

When moving through the autocomplete selection list distinguish between
the following cases:
1) When there is no autocomplete window open, only open one and select
the first item when the CompleteOrPrevSelection /
CompleteOrNextSelection actions are emitted (e.g. by pressing SHIFT +
TAB, TAB)
2) Otherwise navigate through the selection list (e.g. SHIFT + TAB, TAB,
UP, DOWN)

- Remove references to raw keyboard events in autocomplete.ts
- Clarify the purpose of startSelection (previously onTab)

Signed-off-by: Clemens Zeidler <clemens.zeidler@gmail.com>

src/KeyBindingsDefaults.ts

@@ -161,27 +161,27 @@ const messageComposerBindings = (): KeyBinding<MessageComposerAction>[] => {
 const autocompleteBindings = (): KeyBinding<AutocompleteAction>[] => {
     return [
         {
-            action: AutocompleteAction.ApplySelection,
+            action: AutocompleteAction.CompleteOrNextSelection,
             keyCombo: {
                 key: Key.TAB,
             },
         },
         {
-            action: AutocompleteAction.ApplySelection,
+            action: AutocompleteAction.CompleteOrNextSelection,
             keyCombo: {
                 key: Key.TAB,
                 ctrlKey: true,
             },
         },
         {
-            action: AutocompleteAction.ApplySelection,
+            action: AutocompleteAction.CompleteOrPrevSelection,
             keyCombo: {
                 key: Key.TAB,
                 shiftKey: true,
             },
         },
         {
-            action: AutocompleteAction.ApplySelection,
+            action: AutocompleteAction.CompleteOrPrevSelection,
             keyCombo: {
                 key: Key.TAB,
                 ctrlKey: true,