Fix/multiple complex property projection

[cyl102]

Hi,

I noticed a bug when selecting multiple Complex properties using the Select statement. Problem is it was using the name of the complex class as the name of the property so that the dictionary will have duplicated keys when selecting multiple complex properties. Instead I tried to create a new unique name by combining the ComplexProperty name with the Property of the Complex object.

I also added a "as" syntax so you can pick your own property name in projection. This also works for simple property selection.

I have also attempted implement a very small portion of the aggregation section of the ODATA specification.

This change supports for example "?$apply=aggregate(Age with min as MinAge,Age with sum as TotalAge)")"

Unfortunately I couldn't figure out how to run the MSpec unit tests with VS2017, so instead I wrote my tests with nunit in the same spirit as the MSpec tests.

I am hoping to have "groupby" working, which is what I really wanted to achieve but its quite difficult.

I also updated .Net version to .Net 4.6.2.

Thanks,

Bobby