Added the Dataaccess to the graph.

The idea is that we store in each edge a pointer in the DataAccess file,
so that we can fetch the name when necessary. The translation from name
to index is meant do be done at line 137 of the file
src/main/java/com/graphhopper/reader/OSMReaderHelper.java

The added integer was then propagated to all the subsequent function calls,
and tests were also updated