Infer better types for most used functions and methods

[ilevkivskyi]

These functions/classes/methods require better stubs (and most of them likely a plugin):

• [ ] Table (+ likely a plugin)
• [ ] Connection, Index
• [x] Column
• [ ] RowProxy, ResultProxy
• [x] Integer, String, DateTime
• [ ] select, insert, update, where, join (+ likely a plugin)
• [ ] and_, or_, func (+ likely a plugin)
• [x] relationship
• [ ] UniqueConstraint, ForeignKey
• [ ] create_engine

[ilevkivskyi]

Solving #9 will help with some of these.

[ilevkivskyi]

select may be the most complicated here because of a weird (from typing point of view) signature -- it accepts fixed length lists:

s = select([users, addesses])
t = select([users.c.id, users.c.name])