[BUGFIX] Use TYPO3 jQuery in Backend

Instead of using the external jQuery library from Google the
jQuery library provided by TYPO3 is loaded.

Change-Id: Ibb07cbf4202ae1b90f32e4bf32de40ef51d478e5
[TASK] Overlayable temlate path configuration

The template path configurations are split into overlayable default
template paths (e.g. plugin.tx_powermail.view.templateRootPaths) and
into a standalone template paths that are used for StandaloneView
instances that can not handle path overlays (e.g.
plugin.tx_powermail.view.standalone.templateRootPath).

Change-Id: Ia39f6ff913537a50543c4384ef9ee3a6395faa26