Changed type for inserted values to DatabaseExpression

This makes the command builder much more flexible.
Parameters no longer set in CreateCommand()

Parameters must be set by the method using the command builder.
Implemented creation of INSERT command
Created a TableMap class
Changed GenerateStructure to CreateMap

CreateMap returns a TableMap object instead of a TableDescription.
Implemented Add()
Added a 'DROP TABLE' command builder
Added SQLite implementation of 'DROP TABLE'
Replaced DeleteTable with 'DROP TABLE' command builder
Removing un-needed usings