<sql-query> and <loader> support

[jagregory]

[jeremylcarter]

What is involved in getting Sql Query to work? I am interested in helping out.

[jagregory]

Adding <sql-query> support would be a fairly large task, not in terms of difficulty just breadth as it'll touch FNH end-to-end.

Completely new mappings require the following steps:

1. Create Builder/Part class for the fluent interface
2. Add methods to the builders that can contain the mapping (for example a property can be within a class, a subclass, a join, etc...)
3. Create the "mapping" class, this is the semantic model representation of the mapping. This is instantiated and populated by the builder
4. Create the mapping serializer, this transforms our semantic model into NHibernate's XML format
5. Test all of the above!