Convert to a multi-module project and implement SesameJena

The commits in this pull request converts the project to a multi-module structure. There is a new common module that is used by both jena-to-sesame and sesame-to-jena.

This commit also contains an implementation of the SesameJena functionality that was previously missing to wrap a Jena Model inside a Sesame Graph interface.

I removed the .classpath, .settings, and .project files that should be temporary Eclipse files outside of source control to minimise conflicts between different developers. They can be regenerated using mvn eclipse:eclipse or using M2E, but they will be ignored by .gitignore after they are regenerated.

The sesame version is also bumped to 2.6.5.