Tear down active transactions in functional test cases

Fix drivers' exec() method to not execute via prepared statements

[DBAL-2623] Fix Generic SQL Sharding Support documentation example

HHVM testing needs to be in PHP 7 mode

Fix fetching last insert ID for sequences on SQL Server

Fix date diff test

Fix CREATE/DROP DATABASE support on SQL Server

[DBAL2626] Add PHPUnit config for continuousphp Oracle testing

Fix "application_name" test on PostgreSQL < 9.2

Run SQL Azure related tests conditionally

[DBAL-2427] Fix negative default value introspection on PostgreSQL 9.4

Prepared statements become unusable after calling closeCursor() on IBM DB2, Oracle and MS SQL Server.

- Suspend HHVM testing until the following items are resolved
  - HHVM PHP 7 mode issues.
    - facebook/hhvm#7626 php 7 mode not recognized by composer as PHP 7
    - facebook/hhvm#7198 type annotations on internal functions, `expects parameter 1 to be _______, null given`
    - facebook/hhvm#7544 HHVM INI settings for PHP7 mode `php 7 is not the same as php 7.1`
  - Trusty Container issues (currently beta)
    - https://github.com/travis-ci/travis-ci/issues/6842 - MySQL socket issue on Trusty beta Container (assume fixed sometime after 1Q17)
- Add line to Force hhvm PHP 7 mode for future testing
  - HHVM fails on composer `This package requires php ^7.0 but your HHVM version does not satisfy that requirement`
  - reference for change https://docs.hhvm.com/hhvm/configuration/INI-settings#php-7-settings

[DBAL-2546] Fixed the failure of `Functional\StatementTest::testReuseStatementWithParameterBoundByReference()` on ibm_db2

The test is partially skipped due to:

1. Fetching blob as binary string from pdo_sqlsrv requires using `PDOStatement::bindColumn()` and `PDOStatement::fetch(PDO::FETCH_BIND)` which are not supported by the DBAL.
2. Setting encoding on the connection level is not supported: https://msdn.microsoft.com/en-us/library/ff628164(v=sql.105).aspx

[DBAL-2546] Fixed the failure of `Functional\StatementTest::testIncompletelyFetchedStatementDoesNotBlockConnection()` on pdo_mysql + libmysql

The test case being fixed should reset shared connection during teardown as one if its methods modifies connection attributes.

Mysqli: Allow secure connections using SSL

The current driver has no option to allow the usage of SSL connections on mysql. I've used the same name params as mysql client.
An example of mysql client usage would be:

mysql --ssl-ca='path_to_ca.pem' --ssl-cert='path_to_client_cert.pem' --ssl-key='path_to_client_key.pem'

refactor secure connection as params

remove space

add space

refactor secure connection

rename method

rename method

docs: add ssl params to use in mysqli driver

rename test method

refactor method setSecureConnection

fix bug

add comment to method

remove string escaping

MasterSlaveConnection::connect: Remove dead code