add summ functions

handle H = []

handle case when H =[]

always call snjac

Always call snjac when derivative info is missing from user-provided
information.

Use an anonymous function

Warm start updates for sqsolve and snsolve. Minor updates to examples

Array bounds added

Array bounds added to lhs of assignments.

Added check for userfun.

userfun can be string or function handle.

Make computing derivatives more efficient.

Added needF, needG to snwrapper so computing derivatives is more
efficient.  The user can check nargout to determine if the derivatives
are needed.

Misc