Safer build updates

[HebaruSan]

This is #3108, minus:

• The AWSSDK upgrade, because it broke the Inflator (see [Bug] netkan.exe no longer able to successfully use IAM  #3112)
• The switch from packages.config to PackageReferences, because it created build files outside the _build folder and broke builds when switching from one branch to another
• The SharpZipLib update, because it gave me some errors about 'ZipFile': type used in a using statement must be implicitly convertible to 'System.IDisposable'. 🖕
• The CommandLineParser upgrade, because it created an inconsistency in which version of the library we're using (Netkan was upgraded, CmdLine wasn't; let's hold off till everything is ready)

Now some things are upgraded but everything should still work. The original motivation of being able to open Core in Visual Studio is probably satisfied, as most of those changes are preserved.

@techman83 can you please try building this and see if it works in the Inflator?

[techman83]

Looks to be working!

447 [1] DEBUG CKAN.NetKAN.Processors.QueueHandler (null) - Initializing SQS queue handler
489 [1] DEBUG CKAN.NetKAN.Processors.Inflator (null) - Initializing inflator
707 [1] INFO CKAN.KSPManager (null) - Loading KSP instances from registry
749 [1] INFO CKAN.NetKAN.Processors.Inflator (null) - Using user-supplied cache at /home/netkan/ckan_cache
1169 [1] DEBUG CKAN.NetKAN.Processors.QueueHandler (null) - Looking up URL for queue Inbound.fifo
1319 [1] DEBUG CKAN.NetKAN.Processors.QueueHandler (null) - Looking up URL for queue Outbound.fifo
1329 [1] DEBUG CKAN.NetKAN.Processors.QueueHandler (null) - Queue URLs: <>
1330 [1] DEBUG CKAN.NetKAN.Processors.QueueHandler (null) - Looking for messages from <>

[techman83]

From a "doesn't break the inflator" perspective, looks ok to me. But I'm pretty unfamiliar with the Cake/C# build process.