JSON fix: fixed raft warnings flawed logic (CURA-905)
JSON fix: fixed raft warnings flawed logic (CURA-905)

For layer_0_z_overlap we are only sure to overextrude when the overlap is more than the airgap.

Layer height warnings are now based on line widths for raft, because the line widths are way larger than the nozzle size.

Curahelper/Cura,ynotstartups/Wanhao,ynotstartups/Wanhao,hmflash/Cura,fieldOfView/Cura,fieldOfView/Cura,hmflash/Cura,Curahelper/Cura