tidying up the output from CreateReleasePackage - includes delta package
moved logic to detect version from filename to extension method
added a test to ensure you don't create a delta package using a newer base version
only build the delta between this and the last full version
extensions namespaces are annoying
build fix
if delta updates fail, fallback to installing without deltas
tracing to investigate how UpdateManager instances are not being disposed of correctly
log which file cannot be deleted