On Lomiri: always show the printer icon

[sunweaver]

Lomiri does not know about hidden indicator services, so if an indicator is in hidden state, it Lomiri shell shows a cogwheel.

For Lomiri we maybe should not hide the printer but always show it (even if the indicator shows nothing). We could possible add a menu item for evoking some sort of print dialog (which we don't have on Lomiri, but on MATE etc.).

More UI feedback is appreciated.

cc @mariogrip @z3ntu @peat-psuwit @tari01