Teach CTest to submit Done.xml. Submission of this file indicates to
CDash that a build is complete and no more files will be uploaded. It
contains the build id returned by CDash and the current time.
This file is submitted last for a given build when using the
`ctest_submit()` command.
If submitting by PARTS, use `ctest_submit(PARTS Done)`.
Allow CTest script writers to specify additional HTTP headers to be sent
to CDash during submission.
The motivating case for this feature is a corresponding change in CDash.
This will allow projects to refuse submissions from any site not bearing
a valid authentication token.
This adds support for the new cdash API where arbitrary files can be
uploaded to the CDash server. This CDash API communicates via json
files so the json parser jsoncpp was added to the Utilities directory.