Fix missing standard file headers.

Also fix Utf8HeaderTest so it can be run in isolation. Make it be a
BaseTest since this works around issues with Config.load() in the
current state of the Config cache.

Testing Done:
After the Utf8HeaderTest fix:
```console
$ pants.dev test tests/python/pants_test:test_utf8_header
*** Running pants in dev mode from /home/jsirois/dev/3rdparty/jsirois-pants2/src/python/pants/bin/pants_exe.py ***
...
13:51:13 00:01   [test]
13:51:13 00:01     [run_prep_command]
13:51:13 00:01     [pytest]
13:51:13 00:01       [run]
                     ============== test session starts ===============
                     platform linux2 -- Python 2.7.8 -- py-1.4.26 -- pytest-2.6.4
                     plugins: cov, timeout
                     collected 1 items

                     tests/python/pants_test/test_utf8_header.py .

                     ============ 1 passed in 0.30 seconds ============

13:51:20 00:08     [junit]
13:51:20 00:08     [specs]
               SUCCESS
```

CI went green here: https://travis-ci.org/pantsbuild/pants/builds/44506276

Bugs closed: 879

Reviewed at https://rbcommons.com/s/twitter/r/1519/
Sync of https://github.com/pantsbuild/pants/commit/9da876e54670b4071956fed5c71478f3269b750d