Primary key detection

[satano]

Closes #156

• If model has primary key specified by attribute and also has a property with conventional name of the primary key, only attributed property is considered.
• If primary key is composite, all of its columns must have order specified and this order must be unique for every column.
• If primary key is composite and the key name is specified, this name must be same for all the columns.
• If primary key is composite, all of its columns must have AutoIncrementMethodType set to None.