Move src/ext into src/openmap/src/main/java/

For Maven. These sources need to be there if they are to be
included in the compile. Otherwise they'd need to each be
built as an artifact, deployed to Maven Central, and include as an
external dependency in OpenMap.
Add Maven pom.xml
Use jboss Maven repo for jai-codec

This will be a problem for publishing to Maven Central which
does not like use of third party repos. The problem is that
jai-codec is not hosted in Maven Central due to license
restrictions.