[AG-23] Should fetch Scala dependencies from other Maven repositories

[felipead]

I've found hundreds of Scala dependencies referenced in an specific organization that are not found in the Maven Central repository (http://central.maven.org/maven2/).

These dependencies are fetched from the following Maven-compatible repositories, which are assigned to the resolvers attribute inside the SBT configuration:

• http://repo.typesafe.com/typesafe/releases
• https://oss.sonatype.org/content/repositories/releases
• https://clojars.org/repo
• https://dl.bintray.com/tpolecat/maven
• https://dl.bintray.com/typesafe/maven-releases
• https://dl.bintray.com/scalaz/releases
• https://dl.bintray.com/kanterov/maven
• https://dl.bintray.com/tpolecat/maven
• https://dl.bintray.com/bintray/jcenter

All these repositories follow the standard Maven repository structure, so it is just a matter of generalizing the Maven2PackageRegistry class to work with any standard Maven repository URL (also, rename it to just MavenPackageRegistry). We can have a list of Maven repositories and search all of them until we find the artifact we're looking for.