Require PHP 7.1

Connection: Support IS NULL in update/delete criteria

If you pass a null to the where array of update or delete it's
pretty obvious what you want.

Most (all?) databases won't match anything if you actually try
to compare with NULL making this a silent failure without it.

fixed array declarations

Correct param comment

The param comment is currently set to string, which is wrong.
The correct hint would be integer/int

Fixed all array declarations inside Driver dir

Correct classes referenced in the Driver implementation details in the documentation

One class missed and one non-existing in example at "Supporting Other Databases" page.

Normalize method signatures for `fetch()` and `fetchAll()`

Wrong class used in documentation - referenced `Driver` instead of `Driver\Connection`

At lest it looks like one to me.

Table->getColumns() performance

Fix type annotations for quote() of Connection interface

Optimize and improve parameter conversion in OCI8Statement

1. Reworked the parser syntax to use proper Oracle escaping syntax as '' instead of \'.
2. Moved valid tests to the Functional section to ensure correct SQL syntax and logic.

Single drivers get and return various types in quote(), the
interface docs should reflect that.

Update git submodule "docs/en/_theme"

This applies the following fixes to DBAL web docs:

- Fix broken ServerGrove image on footer
- Fix occasional link overlap
- Delete .DS_Store file in bootstrap folder
- Finish PR #3 "<ol/> styles fixed" (margin-bottom)
- Fix <ol/> styles
- Synchronize docs layout menu with main site.
- Show versions only when having more than one.

Fixed oracle bug that primary key is missing if index_name != constraint_name

SQLParserUtils::getPlaceholderPositions fails if there are quoted strings containing only backslashes