Initial support for contact tasks - basic collision detector and everything around
Initial task for stringer strike
Fix contact detection fail when working with 'sparse' meshes
Minor updates to 'tasks/demos/stringer-strike.xml' to make it usable
Multiple fixes for contact-related algorithms, make them working
Parallel impl of contact algos - dirty but working
Add basic tests for P-wave and S-wave on free sliding contact
New nodes and tetrs storage management
Add support for setting default contact border type in task config file
Remove excessive logging from 'InterpolationFixedAxis' on 'debug' log level
Update tests for basic contacts (P-wave and S-wave on adhesion and sliding border)
Fix misprint in 'threshold' term
Add setting contact threshold in task config file
Add clear contact state for nodes between time steps
Better logging