Expose static parameters and xml docs of type providers

[fsharp]

Expose static parameters and xml docs of type providers

Yes, makes sense

@ovatsus The XmlDoc for provided types should already be populated - are you seeing that?

[ovatsus]

In the FSharp.Data.xml file generated by the compiler there's no mention of any of the type providers:

• CsvProvider
• JsonProvider
• XmlProvider
• FreebaseData
• FreebaseDataProvider
• WorldBankData
• WorldBankDataProvider

The XmlDoc property of the FSharpEntity instances has the comments, but the XmlDocSig property is empty. We're looking for <param> tags there to discover the parameters, but it's a very unreliable way to get the info. You don't get the type of the parameters, the default values, or event the parameters for which there's no documentation. See ovatsus/FSharp.Formatting@a5c6c06#diff-e2212151e1f9b6e7e085820d2a6b71caR572

[ovatsus]

Ah, turns out staticparameters were already there, I missed them. The DefaultValue and IsOptional fields you added are working, but HasDefaultValue is coming always false, even when there is a default value and its correctly populated in the DefaultValue field. I still have to hack around the xml docs, though...

[ovatsus]

As HasDefaultValue is not working, maybe you can remove it, IsOptional is already a good indicator ovatsus/FSharp.Formatting@d6ec05f#diff-e2212151e1f9b6e7e085820d2a6b71caR441