[Bug 33353] Keyboard shortcut should be able to accept [WindowsKey] + [Another Key]

[Luna-Tick]

Public bug reported:
https://launchpad.net/malone/bugs/33353

Affects: control-center (Ubuntu)
       Severity: Normal
       Priority: (none set)
         Status: Unconfirmed

Description:
I am pretty sure that this is where I am meant to put problems in the
Keyboard Shortcuts found in Breezy, but please re-assign if necessary.

I like to be able to use my Windows Key as a command key and set
[WindowsKey] + L to locking the screen. It annoyed me to find out that,
when I went into System > Preferences > Keyboard Shortcuts and clicked
on lock screen, I could only set it to either "Super_L" or L and not a
combination of the two.

I would suggest that the key be 'bound' when they are released, so that
it is recognised if people are trying to allocate a combination of keys
to a function.