Feature request: make time-dependent view optional

[jkirk]

I just stumbled over this cool parking lane viewer.

It took me quite a while to figure out that the viewer is time-dependent and parking lanes are not shown when parking:condition:left:time_interval is set and the current time is out of it. And as its Sunday today quite some parking lanes were not shown and it took quite a while to figure out why (after I found https://github.com/zlant/parking-lanes/issues/19)

Please consider making the time dependency optional or add another legend were parking lanes with time_interval set are shown anyway.

Thx for this cool project!