Re-Build Single Jobs

[SmokinCaterpillar]

AppVeyor offers only a button to re-build an entire commit, but also being able to re-building single jobs of a particular commit would be very helpful.

From time to time single jobs fail not due to erroneous code but due to other circumstances. For instance, a connection may time out when cloning a
repository or the 40 minutes limit may be occasionally surpassed. Thus, instead of re-building the entire commit because of a single job failing, it would be very helpful to just restart this particular job to save time and resources.

Btw, Travis has this feature already ;-)

[FeodorFitsner]

OK, great suggestion. Thanks!

[stoivo]

Are we getting anywhere?

[sharwell]

This would be very helpful. What's frustrating is cases where only 1 job (of 4) failed, which means the other three submitted coverage information to codecov.io. When I rebuild the entire matrix, on top of taking 4x as long, I end up with a code coverage report with 7 jobs instead of the expected 4 (3 from the original build, plus 4 more when I rebuild the matrix).

[IlyaFinkelshteyn]

Closing in favor of #58