Allow to override default types with length or precision parameters

[bahusoid]

It's possible since #702 to override default type with custom type. But current solution is limited as it doesn't handle precision or length based types.

So this PR aims to fix this limitation and it allows:

1. Transparently replace any default type with custom type (with exception for places where explicitly NHibernateUtil.SomeType is used like IQuery set param methods SetString, SetDateTime,...)
2. Simplify custom type mapping by reusing existing length, precision and scale mapping attributes.

Example of string override:

//Somewhere before SessionFactory is created
TypeFactory.RegisterType(
	typeof(string),
	new CustomStringType(),
	new[] {"string"},
	configurator => configurator.SetTypeByLengthOrScale(length => new CustomStringType(length)));

[hazzik]

Why not just like this?

//Somewhere before SessionFactory is created
TypeFactory.RegisterType(
	typeof(string),
	new CustomStringType(),
	new[] {"string"},
	length => new CustomStringType(length));

//Somewhere before SessionFactory is created
TypeFactory.RegisterType(
	typeof(string),
	new CustomStringType(),
	new[] {"string"},
	(scale, precision) => new CustomStringType(scale, precision));

Why do we need TypeConfigurator?

[bahusoid]

To avoid public methods multiplications. In 6.0 it's going to be single public method which looks cleaner to me. Also it simplifies further extension - you can add any number of members to TypeConfigurator without breaking changes and still have only single public method exposed.

Well... If you are not convinced can make two additional methods as you suggested.

[hazzik]

and still have only single public method exposed.

I don't mind having a method overload.

[bahusoid]

I don't mind having a method overload.

Overloads with delgates tend to collide so I prefer avoid such overloads if possible. For instance length => new CustomStringType(length) now is nicely resolved by compiler to GetNullableTypeWithLengthOrScale. But if you want to add some similar delgate with different input parameter like NullableTypeCreatorDelegate - you have to use new method name as overload will be ambigious for lambda calls.

So are you sure with overloads?