updating file properties for self-contained zip deployments

[brettsam]

Fixes #336

The issue here is with the file permissions that get applied after mounting the zip files in our linux hosting environment. Some points:

• When deployed as self-contained, the functions host invokes the application executable directly. (When framework-dependent, it runs dotnet AssemblyName.dll).
• On Linux, this means the file needs execution privileges.
• Our environment uses fuse-zip to mount zip files, which checks each file in the zip and uses it's HostOS value to decide how to apply its ExternalFileAttributes: https://bitbucket.org/agalanin/fuse-zip/annotate/89545b47f19801ca298d37fcf460e4ed311dc6c0/lib/fuseZipData.cpp?at=master#fuseZipData.cpp-158:231.
• Because this flag is set during the zip operation, this is Windows, and the Unix executable properties don't work.

The fix here is to pull in a richer Zip library that allows us to manage that field and make sure it's set to Unix so that fuse-zip can properly apply the executable permissions.