Improve handling OnClick events

[kianzarrin]

see

TMPE/TLM/TLM/UI/SubTools/JunctionRestrictionsTool.cs

Line 157 in 3d5a286

// prevent accidential activation of signs on node selection (TODO improve this!)

EDIT: also see

TMPE/TLM/TLM/UI/SubTools/VehicleRestrictionsTool.cs

Line 94 in 3d5a286

MainTool.CheckClicked(); // TODO do we need that?

and see #721 (review)