…Scanner'

 instead of maven-filtering

In exchange for some extra file management code, this reduces the amount of dependencies
used and injected into AsciidoctorMojo. It should also speed up build times since we
are doing much less work now to copy resources.

* Created model classes for Resources to ensure Mojo descriptors don't leak internals
* Remove 'org.apache.maven.shared:maven-filtering' dependency
* Bump plexus-utils to v3.3.1
* Remove unnecessary IT 'resource-filtering' since "under-the-hood" filtering is no longer possible

* Remove unused encoding from resource processing
* Created CopyResourcesProcessor
* ResourcesProcessor no longer throws MojoExecutionException