Move InputLocation/InputLocationTracker/InputSource to velocity templates

- Updated velocity templates in src/mdo/java/ to support Maven-specific features
- Added isMavenModel parameter support for importedFrom field and methods
- Added Maven-specific toString format and constructors
- Updated maven-api-model pom.xml to enable locationTracking and generateLocationClasses
- Removed manually written InputLocation classes from maven-api-model
- All Maven-specific functionality preserved through template conditionals

Author: gnodet

api/maven-api-model/pom.xml

@@ -59,6 +59,8 @@ under the License.
           <params>
             <param>packageModelV4=org.apache.maven.api.model</param>
             <param>isMavenModel=true</param>
+            <param>locationTracking=true</param>
+            <param>generateLocationClasses=true</param>
           </params>
         </configuration>
         <executions>