Continuation Core and Toolboxes (COCO) Code

added infinite loop detection to reverse communication in locate_events

- we now use 3rd order Hermite interpolation for locating singular
and multiple events -> much more accurate and convergence test
is now robust
- the event handler (if present) now issues a warning if a special
point could not be located, this removes unnecessary warning
messages

moved test of event function value to locate_multi

- we now use scaled estimate of interpolation error for
error test in locate_multi
- added opts.cont.MEVFac for customising acceptance of
multiple events
- corrected evhan for cusp and pitchfork (now includes
error handling)
- fixed bug in locate_events: "touching zeros" are now
treated correctly
- we don't allow strings for function handles anymore
- added example (unfolded) pitchfork

set ignore list

added directory for example pitchfork