refactors the low-level classes related to jdt.

1) moved classes to new package spoon.support.compiler.jdt
2) moved internal classes to top level types for facilitating extensions of Spoon

git-svn-id: svn://scm.gforge.inria.fr/svnroot/spoon/trunk/spoon-core@2363 b1f50995-73fd-43b8-8ca2-fbc405a04e82