Reduce number of API requests during deploy

For every class name, a request is made to the API server to retrieve
the package to which it belongs. This is unnecessary, since a package
contains a list of the classes it owns. This patch adds a second cache
to PackageClassLoader that maps class names to the package, and reduces
the number of calls for the io.murano classes to 1.

The second improvement is to add blank YAML definitions for system
classes (the function definitions are in python code) which allows
the engine to cache those, too.

Change-Id: Iee3c39b7c4965d5b8015d458afb78c324dfd2826
Merge "Reduce number of API requests during deploy"