Continuation Core and Toolboxes (COCO) Code

- new function coco_get to access settings for toolboxes in a tree-like way
- coco_set and coco_get allow access of toolbox settings using the prefix
as a path; settings are recursively inherited from the leafs to the root
making it possible to have more general and more specialised settings; in
particular, to set options for each instance of a multiply present toolbox
- cleaned up the toolboxes alcont, pocont and mh_imfcont; these toolboxes
now use much fewer files and use the new coco_set/get functionality; many
functions added with add_func are now local to m-files that add them
- new possibility of passing an 'empty' toolbox to coco; the whole continuation
problem can be constructed by the user, see example coneD; this is intended
for toolbox developers to set up and test problems prior to moving code to
toolbox constructors
- fixed a few bugs and removed 'x' from the permissions of all m-files

fixed computation of period-doubling curves

tested different strategies for bandwidth reduction

full testing of variational problems

coco now uses full path for saving -> changing directory during running computation no longer spreads solution files all over the place

added test matrices for demo bandwith reduction

added example mex file; no measurable speed up though

new ToDo file

added preemptive residuum check before adding chart

tested preemptive residuum test in state_update