Adjustments for the `RASqliteColumn`.

Adjusted the implementation for the check, create, and delete methods,
aswell as the related unit tests, to use the `RASqliteColumn` definition
instead of standard `NSDictionary` objects with `name` and `type`.
Implemented simple constraints for the column definitions.
Column constraints.

Added support for various column constraints.
- Unique
- Nullable
- Autoincrement

Also, added a few TODO notes regarding checking and default values.
Added data type check for columns when checking and creating.
Added default values for column constraints.
Fixed issues with column constraints.

Fixed minor bug with autoincrement. Also, changed handling of
default values for the column constraints, since the setter might
trigger an exception depending on column data type.
Added minor TODO note.
Adjusted the structure for the terminal sample model.
Minor adjustments to debug messages and implmented support for nullable/primary key checks.
Last inserted id and row count.

Moved the `lastInsertId` to a new section and implemented support for retrieval
of the number of rows affected by the last query, `rowCount`.
Modified the  enum definition for error codes, log levels and transaction types.
Column type implementation modified.

Modified the implementation for the column and the data type to be
more flexible, with support for both `numericType` and string `type`.
Implemented more support for column default value.
Removed default value for integer/real columns.
Fixed default value handling and simplified table creation code.
Minor adjustments to the sample terminal model.
Updated copyright year.
Added unit tests and documentation for tests.
Issue with transactions fixed.

The pass-by-reference commit variable did not retain the value from within
the block, hence the transaction would not always be committed. This issue
have been fixed by removing the pass-by-reference variable and instead
expects the block to return whether to commit or rollback, as described
within the method documentation.

Also, removed some trailing spaces on blank lines.
Implemented unit tests for transaction, both insert and delete.