Add a New LdapSchema Class that Represents the Full Schema in Use

[ChadSikorra]

Currently the schema is parsed and converted into separate LdapObjectSchema objects and retrieved via a factory. This is not ideal. It also makes it very hard to use the schema in different areas of the library (such as in converters). To fix this the following should happen:

• Create a new LdapSchema class. All parsed LdapSchemaObjects for the schema in use should be contained in here.
• The LdapSchema class should have a setter/getter on the domain configuration. Because ultimately it's associated with the domain connection/configuration.
• The LdapObjejctSchemaFactory will be replaced by a LdapSchemaFactory.
• The schema events will somehow need to be carried over or rethought out.

However, this should ultimately help improve caching, remove the need for the LdapObjectSchema in certain constructors, simplify the code, and allow schema types to be used in the attribute converter process.