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/KeyBindingsManager.ts

@@ -52,14 +52,19 @@ export enum MessageComposerAction {
 
 /** Actions for text editing autocompletion */
 export enum AutocompleteAction {
-    /** Apply the current autocomplete selection */
-    ApplySelection = 'ApplySelection',
-    /** Cancel autocompletion */
-    Cancel = 'Cancel',
+    /**
+     * Select previous selection or, if the autocompletion window is not shown, open the window and select the first
+     * selection.
+     */
+    CompleteOrPrevSelection = 'ApplySelection',
+    /** Select next selection or, if the autocompletion window is not shown, open it and select the first selection */
+    CompleteOrNextSelection = 'CompleteOrNextSelection',
     /** Move to the previous autocomplete selection */
     PrevSelection = 'PrevSelection',
     /** Move to the next autocomplete selection */
     NextSelection = 'NextSelection',
+    /** Close the autocompletion window */
+    Cancel = 'Cancel',
 }
 
 /** Actions for the room list sidebar */