[TASK] Adapt install tool mail functions to use Swiftmailer

The mail sending functions in install tool use PHPs mail() function.
They should use instead the Swiftmailer.

Releases: 6.2
Resolves: #49366
Change-Id: I0d44150a37284804344793bfc34a89847b3ddb4b
Reviewed-on: https://review.typo3.org/21622
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
[BUGFIX] Reports Module links to the standalone install tool

Link to the backend module instead of the standalone version.

Change-Id: Icf32b91c1fe6edb2b3fa313c865441a1edc3a731
Resolves: #49353
Related: #49162
Releases: 6.2
Reviewed-on: https://review.typo3.org/21616
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
[TASK] Add support for "outdated" extensions

Extension Manager displays installed extensions which are marked as
"outdated" with different styling. Reports module also checks for
installed and available "outdated" extensions.

Change-Id: I3050f3f7142e4153954f1b7f76b4bf64a3066223
Resolves: #49350
Releases: 6.2, 6.1, 6.0, 4.7, 4.5
Reviewed-on: https://review.typo3.org/21620
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Xavier Perseguers
Tested-by: Xavier Perseguers
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert
Activate tests for PHP 5.5 on travis

Change-Id: Iff803f329275f17921b26d88eb46d7b323b7c7ee