Fix entry point to point to new run_gui function

[llimeht]

The current entry point defined by setup.py has not caught up with the change to the function name for the entry point:

$ sasview
Traceback (most recent call last):
  File "/usr/bin/sasview", line 11, in <module>
    load_entry_point('sasview==4.2.0', 'console_scripts', 'sasview')()
  File "…/lib/python2.7/site-packages/pkg_resources/__init__.py", line 564, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File …/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2662, in load_entry_point
    return ep.load()
  File …/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2316, in load
    return self.resolve()
  File "…/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2326, in resolve
    raise ImportError(str(exc))
ImportError: 'module' object has no attribute 'run'

with the egg containing in sasview-4.2.0.egg-info/entry_points.txt:

[console_scripts]
sasview = sas.sasview.sasview:run

This patch replaces run with run_gui in the entry point.