Add '.NETFramework3.5-CompactFramework' and `net35-cf` framework monikers

Description

I'm experiencing an issue with a the Antrl.Runtime package but it seems to only happen in a specific repository. When you run paket restore and the package is not in the cache you get the message:

This message is treated as error whereas I would expect it to be a warning. Because this is an error it is causing our CI builds to fail.

Repro steps

Please provide the steps required to reproduce the problem

1. run paket clear-cache --clear-local
2. run paket restore

result:

I created a small repository to reproduce the issue, but inside that repo paket does behave as expected:

Expected behavior

Could not detect any platforms from '.NETFramework3.5-CompactFramework' in Antlr4.Runtime 4.6.4, please tell the package authors
Is logged as a warning to the console

Actual behavior

Could not detect any platforms from '.NETFramework3.5-CompactFramework' in Antlr4.Runtime 4.6.4, please tell the package authors
Is logged as an error to the console

Known workarounds

When the package is in the NuGet package cache, meaning paket does not have to download it, the message does not show. However, since our CI servers are automatically cleaned on a regular basis to save disk space this errors comes back on our servers.

Start by tracing the framework-moniker detection and the paket restore path after paket clear-cache --clear-local. Reproduce the cache-miss behavior with the reported .NETFramework3.5-CompactFramework and net35-cf monikers, then verify that the monikers are recognized and the message is treated as a warning rather than an error.