Add undo, redo, delete and select all commands to context menu

menus/darwin.cson

@@ -195,6 +195,10 @@
 
 'context-menu':
   '.overlayer':
+    'Undo': 'core:undo'
+    'Redo': 'core:redo'
     'Cut': 'core:cut'
     'Copy': 'core:copy'
     'Paste': 'core:paste'
+    'Delete': 'core:delete'
+    'Select All': 'core:select-all'

menus/linux.cson

@@ -148,6 +148,10 @@
 
 'context-menu':
   '.overlayer':
+    'Undo': 'core:undo'
+    'Redo': 'core:redo'
     'Cut': 'core:cut'
     'Copy': 'core:copy'
     'Paste': 'core:paste'
+    'Delete': 'core:delete'
+    'Select All': 'core:select-all'

menus/win32.cson

@@ -172,6 +172,10 @@
 
 'context-menu':
   '.overlayer':
+    'Undo': 'core:undo'
+    'Redo': 'core:redo'
     'Cut': 'core:cut'
     'Copy': 'core:copy'
     'Paste': 'core:paste'
+    'Delete': 'core:delete'
+    'Select All': 'core:select-all'