Bump FSharp.Compiler.Service to 0.0.0.20
Bump addin version to 3.2.24
Update language service with latest FSharp.Compiler.Service API changes
Update HighlightUsages with latest FSharp.Compiler.Service API changes
Update ReferenceFinder with latest FSharp.Compiler.Service API changes
Merge pull request #334 from 7sharp9/master

Bump FSharp.Compiler.Service to 0.0.0.20 and address API changes