resourceloader: Fix broken getRequest/getDirection in derived context

resourceloader: Fix broken getRequest/getDirection in derived context

getDirection() isn't a simple getter value like the others. It actually
is tightly coupled with getLanguage() and lazy-initialised.

When calling setLanguage(), we shouldn't reset direction back to the
parent class but make sure getDirection() will recompute it based
on the local value.

Added regression test (which fails without this patch).

The parent getDirection() looks for $this->request, but the subclass
doesn't assign that member in the constructor. getRequest() forwards
it accordingly, so make sure getRequest() is also used internally.

Change-Id: Ifec703647368c3bb58748288ed754aaaf3730e19