Made updates to the *.py files so they can work in Spyder and general updates for Python 3

• Edits to print and error calling syntax. Replaced StandardError with call to sys.exit(). xrange() replaced with range()
• Includes code to check if there is an issue accessing the custom ostim pointprocess (which had briefly happened to myself and another model user).
• Now, any time in the code that the h submodule is imported, the stdlib.hoc and nrngui.hoc libraries are also loaded
• works in Spyder except haven't checked past the mayavi part as not currently installed in my environment