Added initial version of stringExtras.

Added a mostly working string.split() function.  This function doesn't
handle end of string issues correctly and is as yet uncommented/undocumented.
Added string.startswith and string.endswith
Finished string.split and added some documentation to the code.

string.split seems fairly solid.  I've tested it out somewhat, but it
returns a non-sequentially ordered vector of strings.  I don't know if
that's just the way resizing domains work or if there's a way to keep
the domain ordered.  Still learning the language.
Merge branch 'string' into develop - Adding a few string functions to develop.

Nothing major yet, but I wanted to get something solid merged into the develop branch.
Still working on string functions.