Add an option to allow a build to not fail if a report is not present.

Adds a toggle to each link section to select if you wish to allow
a report to fail if it is unable to find the source file.
Only publish report if it is present.

Only create the links if there is something to archive. This should
complete the use case of having matrix jobs and only publishing
reports for one matrix job.
Merge pull request #12 from hubnerd/master

Add an option to allow a build to not fail if a report is not present.