Added missing System.Core reference to FSharp.Data.

These references are necessary in order to correctly build FSharp.Data
on Mono/Xamarin Studio.
Merge pull request #130 from jamesholwell/master

Added guard to file resolver to support Mac absolute paths
Merge pull request #128 from diegofrata/master

Added missing System.Core reference to the projects.
Allow to access the underlying csv row representation without using reflection
Fix escaping problem in csvprovider xmldocs
Fix documentation unit tests (duplicate variable names in http.fsx)
Hide .ToString(), .GetHashCode() and .Equals() from Xml and Json generated types (EditorBrowsable doesn't work correctly in F#)
The schema separator should always use commas, and not the separator of the main file (that was what was in the docs, and it's more intuitive)
Use tabs by default if the file extension is .tsv (fixes #54)
Support for Guid  type
Use the generated row type instead of the erased row type in the CsvFile generic parameter to allow to preserve it in higher order functions (the TryFSharp version does the same)
Default sources for world bank provider were wrong + Reduce number of big unit tests
Operations for transforming csv files
Also detect separator from file extension in dynamic CsvFile
Memory usage improvement + report line numbers correctly
Allow to disable caching of rows to support large datasets
Fix path resolution when using the sample data at runtime
Performance improvements (reading a 500000 lines csv goes from 39.4s to 13.4s)
Update readme
Update signature tests