Use the same namespace pattern for assembly/component format as the rest of Maven

Currently, the namespaces are

http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2

and

http://maven.apache.org/plugins/maven-assembly-plugin/component/1.1.2

but Maven and Site Decoration Model use this pattern:

http://maven.apache.org/POM/4.0.0

and

http://maven.apache.org/DECORATION/1.4.0

We should adapt this pattern and rename the namespaces to

http://maven.apache.org/ASSEMBLY/1.1.2

and

http://maven.apache.org/COMPONENT/1.1.2

or better yet

http://maven.apache.org/ASSEMBLY/COMPONENT/1.1.2