Add the toggle command to the command palette
Remove command from main application menu

Since most packages add their commands to the command palette, I find
that I always look for this command first in the command palette, only
to then realize that it's not there; it's in the application menu
instead. Well, let's change that.

This commit removes the command from the application menu.

36f7748 adds this command to the command pallete.
Don't override OS X's built-in Command+` shortcut

OS X uses Command+` for switching windows inside an application [1]. If
a Sublime package binds an operation to Command+`, you cannot use the
standard OS X keyboard shortcut to switch windows inside Sublime.

Since I use the command palette to trigger this command (36f7748), I
don't need the keyboard shortcut. So, remove it.

[1] http://support.apple.com/kb/ht1343