Added POST possibility to WebUserAgent.

Also implemented Package Verification to use POST because this hopefully fixes an
issue with some proxies and many packages.
Extended tests, named tests, improved POD to specify ArrayRef option, test for Data.
Fixed HTTPS urls through proxy servers.
Added HTTPS get test.
Added POST functionality to WebUserAgent. Fixed usage of HTTPS proxies.

Also moved PackageVerification to use POST instead of GET.
Added more tests to both Package.t and WebUserAgent.t.