do not highlight tiles that cannot be placed but don't block selection

[SimplyLiz]

In EventManager, all Nodes in a selection are added to m_nodesToHighlight and highlight gray (can be placed) or red (cannot be placed).

There are certain cases (zones / roads) where we allow to select tiles were placement is not possible (already occupied or slopes) but we don't block the other placement for convenience.

To better visualize that those tiles will not be replaced, those nodes should not be highlit. (not added to the m_nodesToHighlight vector)

[Mograbi]

didn't understand this quit right. can someone explain it better ?