Describe sections in the CAST Manual and keep sample inputfile "CAST.txt" up-to-date

[S0S-90]

There are a few tasks in CAST that are not (or not sufficiently) described in the manual. These seem to be:

• NEB (is currently used in our working group, so very important!!!)
• GOSOL
• STARTOPT (especially the Ringsearch task)
• GRID
• PATHOPT
• PATHSAMPLING
• SCAN2D

So please, if you know something about any of these tasks, write it in the manual for other people who want to use it. Also after implementing new functionality it would be nice to describe it there when you merge it to devel branch. And you should add new options to the sample inputfile "CAST.txt" after implementing them.

[S0S-90]

Tasks NEB and PATHOPT were added by copying stuff from tutorial.

[S0S-90]

Some stuff for SCAN2D has also been added.