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.

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

Add immutable date types

[DBAL-990] Try platform detection without database name as fallback

Closes #1882

FIX Sequence::isAutoIncrementsFor now case insensitive

Merge MySQL 5.7.9 (GA) semantics into MySQL57Platform

Adding PDO as hard dependency as per discussion in #808

Close #713
DBAL-1030

Added missing filtering of table name assets in DB2SchemaManager