Crash when using nonstandard mono location

[fdoyon]

Hardcoded paths in the help service crash when mono is installed in nonstandard locations. Please support the assembly resolve path list as well.

omnisharp-server/OmniSharp/AutoComplete/HelpService.cs

Line 54 in e190291

sources.Add("/Library/Frameworks/Mono.framework/Versions/Current/lib/monodoc/");