* BLD: Fix minimum Python version in setup.py

See https://github.com/numpy/numpy/issues/12480 for discussion.

- Create 1.17.0-notes
- Update index.rst for new notes
- Update pavement.py
- Update setup.py
- Remove Python 2.7 and 3.4 from CI testing.
- Add `# cython: language_level=3` to `*.pxd`, `*.pyx` files.

Note that this removes support for both Python2.7 and Python3.4 in
setup.py.

ENH: Use entry_points to install the f2py scripts.

The text on numpy.org was better, so mostly reused that.
Only kept the additional clarification about wheels on PyPI being
BSD licensed.

closes gh-11793

This adds entry_points for the f2py scripts. The installed scripts
differ between Windows and other environments.

* On Windows, the only script installed is 'f2py'. This works well in
  that environment because each Python version is installed in its own
  directory, making it easy to keep the differing script versions
  separate.

* Otherwise, three scripts are installed, 'f2py', 'f2py' + 'minor', and
  'f2py' + 'major.minor'. For instance, if Numpy is installed by
  Python 2.7, then the installed scripts will be named 'f2py', 'f2py2',
  and 'f2py2.7'. That naming scheme is used for back compatibility, and
  also so that more than one Python version can be dealt with in a way
  common to many Linux distros. Note that 'f2py' will always point to
  the latest install and 'f2py(2|3)' to the latest Python (2|3) install

The script tests have been modified to check for the new environment
and the code previously used to install the scripts has been removed.

The changes introduced in #10463 caused f2py to hang in somde
circumstances. There is may a better fix than this, but
until it is implemented it is better to undo the change.

Closes #11649.

[ci skip]

Fixes #10646

The original intent was to disable builds when _only_ the egg_info target is requested, not whenever it is one of the targets.