Add support for packages to the indexer
This MR allows the indexer to import modules with the same name from different packages. It also adds an inPackage attribute to each entry in the index and displays it on the search page.
As a result of this improvement it is also possible to import different versions of a package. To fix this, only the latest version of a package should be indexed.
Closes the issues #10 (closed) and #11 (closed).
