Support temporal types with EF

[lewischeng-ms]

Now in RESTier, supported mapping options for temporal types are:

EF Type	SQL Type	Edm Type	Need ColumnAttribute?
System.DateTime	DateTime/DateTime2	Edm.DateTimeOffset	Y
System.DateTimeOffset	DateTimeOffset	Edm.DateTimeOffset	N
System.DateTime	Date	Edm.Date	Y
System.TimeSpan	Time	Edm.TimeOfDay	Y
System.TimeSpan	Time	Edm.Duration	N

Reference: https://msdn.microsoft.com/en-us/library/bb386947(v=vs.110).aspx#DateMapping

*Unless all the three types are DateTimeOffset, the time zone would always be assumed +00.00 to ensure the consistency of type conversion.

The basic CRUD and query options are tested with the temporal types. However due to a bug in OData Web API, currently built-in functions (e.g., hour, minute, etc.) on Edm.TimeOfDay cannot work well yet. And due to another bug in ODL, the type annotations of the temporal types in full metadata payload MAY be incorrect.

*Will provide documentation for this feature later.

[lewischeng-ms]

The issue of built-in functions on Edm.TimeOfDay in OData Web API has been fixed by OData/WebApi#614. Thanks @xuzhg !

[lewischeng-ms]

Close first. Will send another one later.