prevent places becoming coarse in petrinets

[Dan Bean]

at the moment if you create a network with the same name as a place, the place appears to become coarse

change update_style() to make the filter for coarse transitions check the node type

[Dan Bean]

fix issue #49 - coarse transition class applied to places if they have the same name as a network

→ <<cset e2ff52a2e9e6>>