Add accessors for InheritanceMap and remove public access
Add support for remapping subpackages in package map

Change data structure to a linked hash map, preserving insertion
order. This allows subpackages to be inserted into the package
map for remapping, before their parent package. For example,
A/B/C -> X and A/B -> Y. With the unordered HashMap data structure,
this was not possible (reliably). With LinkedHashMap, now it is.