/sqlite3cc

- add columns() to row that returns a boost::tuple of various types so multple columns can be fetched at once

	- look in to using BOOST_PP_ITERATE macro

- make basic_statement and database keep a shared pointer to the database handle so the classes can be made copyable. Also:

    - the wrappers around the handle can clean them up after use

    - the actual wrappers wround the handles can be made in sqlite::detail

    - this will also make the implementation od rows (to get round the forced non-dependency of rows on querys) a little easier to swallow.

- move _null_t, _exec_t and _set_index_t to sqlite::detail. Only the named instantiations of these structs need be in the sqlite namespace.

- add immediate_transaction

- committing a transaction during a query (i.e., when sqlite3_step() has returned SQLITE_ROW) causes an error. To counter this:

	- calling query.reset() before the commit fixes the issue

    - need to check it's not fixed in latest sqlite

    - will need to keep a list of querys that need resetting in the database  :o(

- turn on extended errcodes in open() and handle them in sqlite_error

- use sqlite3_db_mutex() to provide extended error information during sqlite_error construction - see sqlite::query::step() for example

- expand sqlite_error - perhaps use boost::system_error (see boost/asio/error.hpp for an example of extending system_error)

- see if we can #include "sqlite.h" in to a namespace.

	Pros:

		we better encapsulate the library

		we can reuse "sqlite3" as a namespace

	Cons:

		makes access to real sqlite stuff awkward to sqlite3cc users, but does this matter? they can't access database._handle anyway!

		potential incompatibility when linking to libraries that also link against sqlite

- fix step() inconsistency - query::step() returns a row, whereas basic_statement::step() and command::step() return an int return code

- query::prepare() isn't being called during construction (form

	basic_statement's constructor)