Modified sliding contact calculator. Negative pressure waves now refract from sliding contact.
Modified panel geo file, added parameter h.
Merge branch 'master' of https://github.com/Amisto/gcm-3d

Conflicts:
	models/panel.geo
Modified sliding contact calculator. Negative pressure waves now refract from sliding contact.
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Contact destruction. The formation of cracks. Multiple initial conditions avalaible.
Crack response via cleaning one stress direction.
Mark in snapshots nodes with outer normal issues
Merge remote-tracking branch 'amisto/master'
Fix backward compatibility with older tasks without *Threshold params
Cleanup crack-related code a bit