Show both "Open File" and "Open Folder" menu on Linux and Windows.

These two platforms do not have a dialog that can select both files and
folders, so we have to use two menu items for two dialogs.

keymaps/linux.cson

@@ -16,7 +16,7 @@
   # Sublime Parity
   'ctrl-N': 'application:new-window'
   'ctrl-W': 'window:close'
-  'ctrl-o': 'application:open'
+  'ctrl-o': 'application:open-file'
   'ctrl-q': 'application:quit'
   'ctrl-T': 'pane:reopen-closed-item'
   'ctrl-n': 'application:new-file'

keymaps/win32.cson

@@ -14,7 +14,7 @@
   # Sublime Parity
   'ctrl-N': 'application:new-window'
   'ctrl-W': 'window:close'
-  'ctrl-o': 'application:open'
+  'ctrl-o': 'application:open-file'
   'ctrl-T': 'pane:reopen-closed-item'
   'ctrl-n': 'application:new-file'
   'ctrl-s': 'core:save'

menus/linux.cson

@@ -4,7 +4,8 @@
     submenu: [
       { label: 'New &Window', command: 'application:new-window' }
       { label: '&New File', command: 'application:new-file' }
-      { label: '&Open...', command: 'application:open' }
+      { label: '&Open File...', command: 'application:open-file' }
+      { label: 'Open Folder...', command: 'application:open-folder' }
       { label: 'Reopen Last &Item', command: 'pane:reopen-closed-item' }
       { type: 'separator' }
       { label: '&Preferences...', command: 'application:show-settings' }

menus/win32.cson

@@ -4,7 +4,8 @@
     submenu: [
       { label: 'New &Window', command: 'application:new-window' }
       { label: '&New File', command: 'application:new-file' }
-      { label: '&Open...', command: 'application:open' }
+      { label: '&Open File...', command: 'application:open-file' }
+      { label: 'Open Folder...', command: 'application:open-folder' }
       { label: 'Reopen Last &Item', command: 'pane:reopen-closed-item' }
       { type: 'separator' }
       { label: '&Preferences...', command: 'application:show-settings' }