Remove the concept of 'integration tests' from test-webkitpy.

Remove the concept of 'integration tests' from test-webkitpy.

There's not really a useful difference between unittests and integration
tests in webkitpy these days, so this removes the integrationtest concept
and renames the files for consistency w/ everything else.

This is being done in preparation for replacing test-webkitpy with the
generic python test runner (by removing nonstandard things from test-webkitpy).

This also removes the custom TestLoader I wrote since we don't need it any more.

R=eseidel@chromium.org
BUG=402172
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=180235

[Dirk Pranke, 2014-08-12 20:53:45]

ping?

[eseidel, 2014-08-13 22:00:03]

The CQ bit was checked by eseidel@chromium.org

[eseidel, 2014-08-13 22:00:04]

lgtm

[commit-bot: I haz the power, 2014-08-13 22:00:40]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dpranke@chromium.org/454223003/1

[Dirk Pranke, 2014-08-14 00:49:57]

The CQ bit was checked by dpranke@chromium.org

[commit-bot: I haz the power, 2014-08-14 00:50:39]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dpranke@chromium.org/454223003/20001

[commit-bot: I haz the power, 2014-08-14 05:09:23]

Committed patchset #2 (20001) as 180235