Removed ungrammatical apostrophes from documentation, replacing
"it's" with "its" where appropriate (but in a few cases with "it is"
when that read better).

While doing that, I also fixed a couple of minor typos etc.
as I noticed them.

Found using: https://github.com/intgr/topy

:class:`.DateTime`.  As Oracle has no "datetime" type per se,
it instead has only ``DATE``, it is appropriate here that the
``DATE`` type as present in the Oracle dialect be an instance of
:class:`.DateTime`.  This issue doesn't change anything as far as
the behavior of the type, as data conversion is handled by the
DBAPI in any case, however the improved subclass layout will help
the use cases of inspecting types for cross-database compatibility.
Also removed uppercase ``DATETIME`` from the Oracle dialect as this
type isn't functional in that context.  fixes #2987

- various improvemnts to oracle docs, rewrite section on unicode, more linking,
enhance section on resolve_synonyms

This feature is now turned off by default.

- clean up some shenanigans in reflection

arguments; [ticket:2866]
- add dialect specific kwarg functionality to ForeignKeyConstraint, ForeignKey

to be very slow.  this now has the effect of producing "conditional" unicode
conversion for the Oracle backend, as it still returns NVARCHAR etc. as unicode
[ticket:2911]
- add new "conditional" functionality to unicode processors; the C-level
function now uses PyUnicode_Check() as a fast alternative to the isinstance()
check in Python