Change fc_nblast so that score matrix must be specified as argument
Change plot3dfc to use nat's default neuronlist as default db
Add example of NBLASTing to quick-start guide
Improve NBLAST test
Fix plotting test by changing to use Kenyon cells
git ignore for vignettes dir
STY: edits to vignette text
Merge branch 'master' of jgit:flycircuit

* 'master' of jgit:flycircuit:
  Fix plotting test by changing to use Kenyon cells
  Improve NBLAST test
  Add example of NBLASTing to quick-start guide
  Change plot3dfc to use nat's default neuronlist as default db
  Change fc_nblast so that score matrix must be specified as argument
give fc_nblast default score matrices again
determine whether normalised score matrices are distance or similarity

* rather than assuming that they must be distance, which is not always true
ignore extdata folder since this will be for downloaded data
reinstate rgl as a dependency and make nat a suggestion

* we need rgl for plot3d generic
* nat is only used in tests
* see dd39dd9b4e96d5c293dd9dda61d018c0911c3622
minor doc fixes/improvements
add optional argument selfun to selectRegionsFromSurf()
simplify selectRegionsFromSurf - also placates check()
ignore extdata folder during build

* since extdata may end up with some large downloaded files.