refactor Users module to use DependencyInjection. refs #1545
refactor Search module to use DependencyInjection. refs #1545
refactor Settings module to use DependencyInjection. refs #1545
refactor Extensions module to use DependencyInjection. refs #1545
refactor Extensions module to use DependencyInjection. refs #1545
revert individual module upgrade routines and handle all in the main upgrade.php file instead.
corrections and split listeners into more descriptively named classes and change service names to match.
CS fixes
Merge pull request #1560 from craigh/dependencyInjection

This PR was merged into zikula:1.3 branch.

Discussion
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Convert system modules to Dependency Injection

When this PR is merged, the profiler will report several errors like "ERROR - Event handler was not attached for event 'get.pending_content' because method 'Zikula\Module\UsersModule\Listener\PendingContentListener::pendingContentListener' is not callable" **this is expected behavior** if (and only if) you are using a development version of the core. Once you reinstall the core or run `upgrade.php` on your original site, this will be take care of. Instead, one can also safely manually delete the `/EventHandler` entries in the `module_vars` table for the **core modules**. if you cannot live with the red errors in your profiler bar.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #1545
| Refs tickets  | -
| License       | MIT
| Doc PR        | -

Commits
-------

0f1646f70b394c8c31796c9f69a952778add3e14 refactor Users module to use DependencyInjection. refs #1545 craigh
116902c7413795c3f78ad09025e481c010445d6f refactor Search module to use DependencyInjection. refs #1545 craigh
1ab0fec14daf306322ebe7013187b2147df768d7 refactor Settings module to use DependencyInjection. refs #1545 craigh
83ac114469a1a7fb5ee078ad3580ae943e1926bb refactor Extensions module to use DependencyInjection. refs #1545 craigh
db2950e507e1ecca7ac0b344dd9c3f2dc2a25ae7 refactor Extensions module to use DependencyInjection. refs #1545 craigh
432c1b2c67c849b75a5cd2e2dbd15453ada67655 revert individual module upgrade routines and handle all in the main upgrade.php file instead. craigh
7851b5b35cafc1f1b47a8bd76fa54a821d104993 corrections and split listeners into more descriptively named classes and change service names to match. craigh
381c3348045bb5e0448fe0e3a037927d12037bfc CS fixes craigh