[FEATURE] Improved Usability & Added DAM-Check

* Usability: In the BE-Module you can now see when the Ext is working
* Feature: You can now delete all or per-check issues from the DB
* Feature: New Check whether DAM-Classes are used in your extensions
[BUGFIX] Cleanup deprecation data
* Updated README to reflect name change
[BUGFIX] Replace Upgrade Report with Smooth Migration
[TASK] Cleanup Checks Definitions
* Move default Definition methods to Tx_Smoothmigration_Checks_AbstractCheckDefinition
Merge remote-tracking branch 'origin/master' into origin/migrate/require_once

* Cleanup doc comments
* Move most methods from migrations to AbstractMigrationDefinition

Conflicts:
	ext_autoload.php