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UnitTest: Added default test suite

- admin folder is excluded
Admin: Disallow file edit

Plugins and themes could be edited in the backend.
Editing files in the backend makes customer crash the page.
Manipulating plugins or themes via backend will be revoked.

- \LeMike_Commons_Admin_Plugins_InstallDate renamed to
  \LeMike_Commons_Admin_Plugins_InstallDateTest
- All test classes shall have the suffix "Test"
Docs: Wiki added to directly change documentation