Amended FarPackage, the installer of FarNet NuGet packages

[nightroman]

It turns out NuGet starting from 4.6.0 does not encode file names as URLs in created packages.
NuGet/NuGetGallery#7955
And the issue is closed as "won't fix".

As a result, System.IO.Packaging originally used by FarPackage misses some files.
E.g. file names with spaces, some symbols, non Latin, etc.
Fortunately official FarNet packages do not use such names.

Thus, FarPackage now uses System.IO.Compression instead and treats packages
as zip files, with some assumptions about the structure. The problem is solved.

FarPackage may handle all files again, good, but it looks like unusual file names are better be avoided.

Commit: 33dcafc