Feature - add bulk_insert

[pussbb]

for e.g.
http://alembic.readthedocs.org/en/latest/ops.html?highlight=bulk_insert#alembic.operations.Operations.bulk_insert
there
This provides a means of representing an INSERT of multiple rows which works equally well in the context of executing on a live connection as well as that of generating a SQL script. In the case of a SQL script, the values are rendered inline into the statement.