Python ``Decimal`` via string is now configurable.  The
flag ``decimal_return_scale`` is now supported by all :class:`.Numeric`
and :class:`.Float` types, which will ensure this many digits are taken
from the native floating point value when it is converted to string.
If not present, the type will make use of the value of ``.scale``, if
the type supports this setting and it is non-None.  Otherwise the original
default length of 10 is used. [ticket:2867]

- other cleanup
- don't need compat.decimal, that approach never panned out. hopefully
outside libs aren't pulling it in, they shouldn't be

- build a new Sphinx extension that allows dialect info
to be entered as directives which is then rendered consistently
throughout all dialect/dbapi sections
- break out the "empty_strings" requirement for oracle test

- begin consolidating docs for dialects to be more self contained
- add a separate section for "external" dialects
- not sure how we're going to go with this yet.

- visit_mods all seemed to not propagate **kw down to process().
this is [ticket:2548] which may be backported to 0.7 pending
a test case to illustrate wrong behavior.