Merge pull request #111 from tpetricek/master

Update NuGet and change FSharp.Data back to .NET 4.0
Remove the #if EXPERIMENTAL madness, it's better to have some duplication
Fix unit tests

Change Freebase tests to use an api key so they work on any machine (fixes #67)
Update expected signature of Freebase, Worldbank and Apiary tests, as the online api has changed
Performance Improvements

The unit test "generating expression works (WorldBank)" went from 55s to 8s
Refactor csv inference to allow testing more parts of the algorithm

The logic that handles the optionals/nullables was mixed with the generation of provided properties, so it wasn't being tested in the inference tests.
Created PrimitiveInferedProperty type to hold the intermediate value between csv type inference and the generation of provided properties and to pass to Helpers.convertValue, instead of passing 3 different values as before
No functionality was changed at all
Generate Nullable<int64> instead of Option<int64> in csv provider to be consistent with int
Improve units of measure support and column naming in CSV Provider

Support SI symbols in addition to SI names
Validate that the measure really exists and ignore it instead of giving errors later
Don't require a space fix between the column name and the '(' of the unit
Improve csv column naming (Fixes #97)
Merge latest changes from sample pack to ProvidedTypes.fs
Properly support namespaces in XmlProvider (Fixes #113)
CSV Improvements (Fixes #19) (Fixes #85) (Fixes #61) (Fixes #95)

Ignore bank lines
Handle duplicate column names and columns with empty names
IgnoreErrors parameter to ignore rows with different number of columns
HasHeaders parameter to allow csv files without header. In this case we look at the first non-empty data row to define the number of columns
Improve uniqueGenerator algorithm to resume numbering if name already ends in a number
Allow to specify the type or type+unit in the header column within braces, like we already allow for units
Schema parameter to override what's inferred form the header and the data rows. Can specify basic type, if it's nullable or optional, units, and column name. Supports overriding only some of the columns
Support for custom quote character
Merge pull request #112 from ovatsus/CsvImprovements

Csv improvements
Merge changes from CSV and XML fixes
Style changes and add some comments