Upstream libs and tools have improvements that make them unnecessary.

By either defining their types or renaming to match parent class (or
interface).

also simplifies the code and now exactly matches postgresql search rules

This reverts commit e3ab1276, reversing
changes made to f988b0a6.

- SERIAL and BIGSERIAL are not true types and can't be used in ALTER TABLE expressions
- When changing between int and bigint auto increment fields the default should no be dropped
  to preserve the link between the column and the sequence.

Serial fields already have a default value. By opting out of `notnull`
serial fields will just set the next value in the sequence.

 Closes #2436

fixes #2270

Fixed inconsistent use of getSQLDeclaration method

Because PostgreSQL will return the expression with a lot of
parentheses we cannot TRIM() them easily. It is easier and more
correct to adapt to what PostgreSQL returns. That means the declaration
of partial indexes must be updated as follow:

Before:
``options={"where": "other_id IS NULL"}``

After:
``options={"where": "(other_id IS NULL)"}``

And fore more complex conditions, that would be:
``options={"where": "(((id IS NOT NULL) AND (other_id IS NULL)) AND (name IS NULL))"}``

This excludes views registered by PostGIS 2.x like geography_columns, geometry_columns, raster_columns and raster_overviews.
The table_name != 'geometry_columns' is kept for PostGIS 1.5 compatibility. The type changed to VIEW in PostGIS 2.0.