AssemblyLoader should assist in loading all assemblies

AssemblyLoader should assist in loading all assemblies

The Resolving event from the AssemblyLoadContext is invoked each
time it fails to load an assembly. The default AssemblyLoadContext
is used internally i.e. when Assembly.Load() or Type.GetType(string)
methods are called. Registering for the Resolving event from the
default AssemblyLoadContext helps handling the unresolved
assemblies and fixes XAML-related issues in Xamarin.

TASK=TNET-136
TASK=TCAPI-1863

Change-Id: I0f5f4c2925829eac448a6184a3e19dbde5c1dfc0
Signed-off-by: Pawel Andruszkiewicz <p.andruszkie@samsung.com>