- Added new 'compiled_cache' execution option. A dictionary

- Added new 'compiled_cache' execution option.  A dictionary
where Compiled objects will be cached when the Connection
compiles a clause expression into a dialect- and parameter-
specific Compiled object.  It is the user's responsibility to
manage the size of this dictionary, which will have keys
corresponding to the dialect, clause element, the column
names within the VALUES or SET clause of an INSERT or UPDATE,
as well as the "batch" mode for an INSERT or UPDATE statement.