Decouple stickyness from alwaysOnBottom/Top

[stefonarch]

I didn't find any open issue about that,but it was mentioned somewhere already.
action name="toggleSticky" and remove it from toggleAlwaysOn*
Maybe this could be also in client menu by default.

Related #856

[tsujan]

This could be used for putting Conly or Qt/GTK widgets (like analog clocks) on all desktops. ToggleAlwaysOnBottom couldn't be used if PCManFM-Qt (or any FM) draws the desktop, because in that case, the window will go behind the drawn desktop once the latter is clicked.

[Consolatis]

We do have a ToggleOmnipresent now (personally I would be fine with adding a ToggleSticky alias which simply triggers the same action). Agree that we should get rid of the on-all-workspaces behavior of ToggleAlwaysOn{Bottom,Top}.

Maybe we could simply have the always-on-top/always-on-bottom scene trees be parented to the workspace trees rather than the layout tree. That should make the code easier rather than trying to update the view stacking order manually.

[tsujan]

We do have a ToggleOmnipresent now

It's nice but, sadly, it didn't work for what I had in mind. The reason is that it makes the window come to the front on switching the desktop. So, for example, when I put an analog clock (or Conky) on desktop and want it to appear on all desktops, I can't use it (I don't want the clock in front of Firefox when the desktop is changed to where Firefox is). Moreover, I can't add ToggleAlwaysOnBottom to the clock because that would easily make it go behind pcmanfm-qt's desktop.

EDIT:
BTW, it didn't work with Conky (xwayland) either.