Do a try import on setuptools then fall back to distutils

If the python has setuptools then use it, otherwise just use
distutils.

Change-Id: Ia240bf90391ae08b359d41cfa47deec3e7e73478
Add setupegg.py which uses ez_setup to get setuptools

This script can be used for creating eggs and wheels.

This setup front end can

Change-Id: Ic12b647f3ed0b14145a0bfb9ff92ab0c04d7468f
When installing the wheel package use ez_setup

Change-Id: I3f2fc1ba88a3b50fd6c5e4b8a62a2eae3dfcef85
BUG: Adding missing cmake error variable for wheel process

Change-Id: I89aec361db7e0191fc936c37a8c1e9afb1099674
Merge branch 'SIMPLEITK-540_DontAlwaysUseEZSetup' into release

* SIMPLEITK-540_DontAlwaysUseEZSetup:
  BUG: Adding missing cmake error variable for wheel process
  When installing the wheel package use ez_setup
  Add setupegg.py which uses ez_setup to get setuptools
  Do a try import on setuptools then fall back to distutils

Change-Id: I7f4981e769a399df0ef75d484e29b740b8bf7998