Implementation of Issue 19

It is implementation of:
https://github.com/AutoFixture/AutoFixture/issues/19

The code is:
a. Throwing more detailed exception in case of usage struct with default constructor (I hope that none of built in structures doesn't fall into this bucket :)).
b. Customization to allow for above situation, properly creating struct and filling all it's fields.

Consideration: 
Class names are slightly longer than average in the project.