Add support for multiple os types

Updates the member snapshot creation code to support multiple os types.
It basically sorts the variants by os type, then applies the code to
optimize the arch properties and then it optimizes the properties that
are common across architectures and extracts any properties that are
common across os types.

The java and cc member types needed to be modified to make the location
of the generated files within the snapshot os type dependent when there
is more than one os type. That was done by adding an OsPrefix() method
to the SdkMemberPropertiesBase which returns the os prefix to use when
there is > 1 os type and otherwise returns an empty string.

Added three tests, one for cc shared libraries, one for cc binary and
one for java header libraries.

Bug: 150451422
Test: m nothing
Change-Id: I08f5fbdd7852b06c9a9a2f1cfdc364338a3d5bac