BoundsError encountered for certain spatial input files

[noemiandor]

Setting Lp to values <1000 gives a BoundsError for certain spatial input files. Whether or not an error occurs may be a function of where the vessels are in the domain.

[noemiandor]

Rather than specifying the length of the domain, one could specify its coordinates (bottom left, right; top left, right). That should allow having scenarios represented where blood vessels don't span the domain.