Enhance support for the Cobertura Coverage Plugin. Deprecates the coverage module.

Increases the amount of recognizable parameters, modularizes existing parameters
and maintains default values.

Modularizes the construction of coverage reports. Coverage reports can now be fully
specified within JJB YAML. Coverage reports now use a default value of zero for
healthy, unhealthy, and unstable. Additionally, at least one target must be specified.

Coverage module gets a documentation and logger warning against its use. Logger object
moved to the head of the code.

Change-Id: I505a6185b3f9005fbbd9786ebdca0ef02ed618f0
Reviewed-on: https://review.openstack.org/28184
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins