[feature/sqlite3] Add support for SQLite 3

Minimum version requirement is 3.6.15 as that's what ships with PHP 5.3.0
when support for SQLite 3 was added.

PHPBB3-9728
[feature/sqlite3] Update docblocks and function visibility

Added missing docblock annotations and added visibility identifiers.

PHPBB3-9728
[feature/sqlite3] Remove trailing comma from column list

PHPBB3-9728
[feature/sqlite3] Fix sql_index_drop() for sqlite3

PHPBB3-9728
[feature/sqlite3] Correctly recreate indexes when recreating a table

PHPBB3-9728
[feature/sqlite3] Remove unneeded ORDER BY type from sqlite_master queries

PHPBB3-9728
[feature/sqlite3] Remove invalid comment

PHPBB3-9728
[feature/sqlite3] Use SQLite3 by default

PHPBB3-9728
[feature/sqlite3] Add sqlite3 database to .gitignore

PHPBB3-9728
Merge remote-tracking branch 'github-nickvergessen/feature/sqlite3' into develop-ascraeus

* github-nickvergessen/feature/sqlite3:
  [feature/sqlite3] Add sqlite3 database to .gitignore
  [feature/sqlite3] Use SQLite3 by default
  [feature/sqlite3] Remove invalid comment
  [feature/sqlite3] Remove unneeded ORDER BY type from sqlite_master queries
  [feature/sqlite3] Correctly recreate indexes when recreating a table
  [feature/sqlite3] Fix sql_index_drop() for sqlite3
  [feature/sqlite3] Remove trailing comma from column list
  [feature/sqlite3] Update docblocks and function visibility
  [feature/sqlite3] Add support for SQLite 3