Fixes to WebMatrix curated feed

[jeffhandley]

Exclude .NET 4.5-only packages from the WebMatrix curated feed

Filed by @jeffhandley

Since WebMatrix only lets you create .NET 4.0-based websites, we should filter packages out of the curated feed if they only support .NET 4.5.

WebMatrix curated feed should also hide packages depending on packages that require Powershell

Filed by @xavierdecoster, fomerly #1311

Example: query for "glimpse".

The Glimpse.Core package uses powershell and isn't shown.
However, quite a few dependent plugin packages that don't use powershell are listed while useless.

Summarizing WebMatrix Compatibility (each bullet must be true)

• MinClientVersion == null OR MinClientVersion <= NuGet 2.2 (current max supported version in WebMatrix)
• IsLatestStable Package
• Contains the tag "aspnetwebpages"
• Does NOT contain ".ps1" or ".t4" files
• Any dependencies WHICH ARE ALREADY ON THE GALLERY, are also compatible.

[analogrelay]

We certainly should!

[analogrelay]

Re: Hiding packages that depend on non-curated packages

Unfortunately, because we allow dependencies on packages that might not exist on the Gallery, there isn't really a reliable way to do this. I'll investigate adding logic to our backend to scan for this condition and fix it, but if Glimpse.AspNet was uploaded before Glimpse.Core we won't be able to tell that Glimpse.AspNet shouldn't be curated solely based on it's dependency.

[analogrelay]

So, the gist of the second item is: We can do this filtering, but ONLY if the dependent package has ALREADY been uploaded. We do in fact do this filtering when those conditions are true. @claycompton, please verify it in that manner when testing. When uploading two packages, A and B, in that order, IF A is otherwise WebMatrix compatible (see issue) EXCEPT that it is dependent upon B which IS NOT WebMatrix compatible, then A is expected to be added to the WebMatrix feed