Update POMs to point to mirror of the cppwrap plugin

This removes the dependency on maven.imagej.net, which has been causing
problems for Travis and Jenkins.
Permit cppwrap failure
Remove docs/release section from the Bio-Formats repository

The download page generation is maintained under a separate
openmicroscopy/ome-release repository so this folder is not needed anymore.
Remove docs/release from the Travis build job
Merge pull request #855 from melissalinkert/cppwrap-mirror

Update POMs to point to mirror of the cppwrap plugin
Merge pull request #862 from snoopycrimecop/rebased/dev_5_0/allow-failures

Permit cppwrap failure (rebased onto dev_5_0)
Merge pull request #863 from sbesson/release_cleanup

Remove docs/release section from the Bio-Formats repository