Add missing Expression overloads for db.Exists<T>, impl currently uses Count > 0
Add ability to choose the particular Oracle client: Microsoft, Devart, or Oracle
with Oracle as the default (used to be Microsoft).

Clean up parameters a bit, more to come. Add some reserved words tests, which
are commented out for now.

Note: don't send them the tests/...Base.cs change as it makes it local to us.
Naming strategy fixes so can limit the length of a name (since Oracle has very
small 30 character limit). Should be submitted as a separate pull request.
Now get last insert works. I think it should use results filter, but I haven't
looked into that in enough detail yet.

And some more fixes.
Trying to make Microsoft provider work too. All same as ODP except for inserting
a float into a field when using Vietnam culture.

Rebase to master after my NamingStrategy changes.

Make foreign keys work.
Remove Oracle.DataAccess.Client reference and use reflection instead.