Support of resource as an SQL script

Currently, it is only possible to specify SQL files (cfr. http://mojo.codehaus.org/sql-maven-plugin/execute-mojo.html#srcFiles). It could be interesting to also support resources. It means introducing a new parameter like "resourceFiles".

That way, a project could rely on another project by specifying SQL scripts contained in the other project by doing something like:

<resourcesFiles>
   <resourceFile>com/myCompany/my-sql-script.ddl</resourceFile>
</resourcesFiles>

where my-sql-script.ddl is a file contained in the classpath.

Currently, we can do that by unpacking the other project in the target directory and referring those unpacked scripts. But that solution is too verbose.