Merge pull request #394 from mastoj/dev

Scriptcs can now load other scripts with relative paths. Fixes #388
Merge pull request #395 from mastoj/dev

test that checks if the IFileSystem.CurrentDirectory has been reset
Refactored IFilePreProcessor to use ILineProcessors instead
Added tests for new files
Hooked up the line processors to ScriptServicesBuilder
Removed path parameter from IFileParser.ParseScript
Made sure that usings are not empty and distinct
Moved guard methods
Moved check for loaded file into FilePreProcessor
Added marker interfaces for default line processors
Added abililty to override default line processors
Renamed UsingStatements and Body to Namespaces and BodyLines
Forgot file when renaming
Some final adjustments
Removed last references to FileProcessorUtil in FilePreProcessor
Merge pull request #396 from khellang/line-processors

Refactored ProcessLine into ILineProcessor
moved Nuget.Core to ScriptCs.Hosting
updated tests to reflect the latest Nuget.Core move to Hosting
Updated some messed up refs in proj files
Removed Nuget.Core