Return real error strings from installd.

Now that we've moved installd to Binder, we can return nice detailed
error strings explaining why a call failed.  This is particularly
valuable when we record the error message into the PackageManager
persistent log, because up until now those errors were limited to
an unhelpful "installd returned -1" message.

Also perform uniform enforcement of all incoming package name and
UUID arguments.

Test: builds, boots, apps install/uninstall fine
Bug: 13758960, 30944031
Change-Id: Ic1f65ce8c10b1329e01d6a49d72cafa879c4d8bc