Fix VS2017 build issue with Roslynator

[mregen]

• vs2017 now only supports .NET 4.6.2 builds, .NET Core 2.1 is end of life.
• Roslynator was not properly excluded in VS2017, change the condition to
• fixes Cannot start reference client in Visual studio 2017 #1630
• fix a few lgtm warnings
• fix a few license headers (everything outside of \Stack is MIT)
• fix flaky Hiresclock test.

[codecov]

Codecov Report

Merging #1641 (5ec231b) into master (a147eb5) will increase coverage by 0.06%.
The diff coverage is n/a.

❗ Current head 5ec231b differs from pull request most recent head 180c65a. Consider uploading reports for the commit 180c65a to get more accurate results

@@            Coverage Diff             @@
##           master    #1641      +/-   ##
==========================================
+ Coverage   53.71%   53.78%   +0.06%     
==========================================
  Files         319      319              
  Lines       57733    57733              
==========================================
+ Hits        31011    31050      +39     
+ Misses      26722    26683      -39     

Impacted Files	Coverage Δ
Libraries/Opc.Ua.Client/OpcUaClientEventSource.cs	55.00% <ø> (ø)
...urity.Certificates/X509Certificate/X509PfxUtils.cs	69.87% <ø> (ø)
...ies/Opc.Ua.Server/Server/OpcUaServerEventSource.cs	46.93% <ø> (ø)
Stack/Opc.Ua.Core/Stack/State/NodeState.cs	42.80% <ø> (ø)
.../Opc.Ua.Server/Subscription/SubscriptionManager.cs	61.34% <0.00%> (+0.14%)	⬆️
.../Opc.Ua.Server/Subscription/SessionPublishQueue.cs	62.69% <0.00%> (+0.31%)	⬆️
Stack/Opc.Ua.Core/Stack/Tcp/TcpMessageSocket.cs	73.72% <0.00%> (+0.34%)	⬆️
...ack/Opc.Ua.Core/Stack/Tcp/ChannelAsyncOperation.cs	68.75% <0.00%> (+1.04%)	⬆️
Stack/Opc.Ua.Core/Stack/Client/ClientBase.cs	71.15% <0.00%> (+1.28%)	⬆️
Libraries/Opc.Ua.Client/Session.cs	64.40% <0.00%> (+1.50%)	⬆️
... and 1 more

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[mregen]

[lgtm-com]

This pull request fixes 6 alerts when merging 180c65a into a147eb5 - view on LGTM.com

fixed alerts:

• 3 for Container contents are never accessed
• 2 for Useless assignment to local variable
• 1 for Invalid string formatting