New suite of tests for headless processing

[timsnow]

This test will check the results generated by a processing pipeline from a stable version of DAWN against the currently nightly build.

There is a short read me and a header in the main script file, validator.sh, which will explain more about how this test suite works.

[jonahgraham]

(I am not really reviewing this, just happened to notice this in the email notification)

@timsnow there are a number of backup files in this PR (files with ~ ending)

@mwebber I notice that dawn-ui has *~ in its root .gitignore, but not dawn-test.

[timsnow]

Good catch, @mwebber would it be a good idea to add *~ to this branch and merge, or would it be preferable to add this directly to master?