Fix code generation and min compiler version

I tried to generate classes for joda-primitives from Eclipse and found two issues:

 - compiler was set to 1.5,
 - file `TestArrayXxxIterator.vm` was not found (I use GNU/Linux, which is case-sensitive).

I've fixed these by changing `<maven.compiler.compilerVersion>` to 1.6 (documentation say Java 1.6 is required) and renaming file to proper case. The project is now buildable from Eclipse on Linux out of the box.