Adds a javascript handler for empty tables

This handler checks if the relevant table is empty and either refreshes the page (or explicitly redirects to the next/previous page) or shows a message.
Adds ajax actions for clipboard items

If a clipboard item's parameters contain `className` and `actionName`, an AJAX proxy action is executed with those parameters and the marked object ids.

This spares us writing that as event listeners for the `clipboardAction` event.

Additional changes:

* Adds `removeArrayValue` function.
* Adds the list item parameters as a third parameter for the event listener on `clipboardAction`.
Fixes function documentation
Adds objectTypeId parameter to ClipboardHandler::hasMarkedItems()

This way, you can check if the user has marked item of the type of objects listed at the current page and not if the user has marked some items of a completely other type you currently don't care about at all.
Text corrected
Merge pull request #541 from Gravatronics/enhancement/clipboard/hasMarkedItemsObjectTypeID

Adds objectTypeID parameter to ClipboardHandler::hasMarkedItems()
Merge pull request #539 from Gravatronics/enhancement/clipboard/AJAXActions

Adds AJAX actions for clipboard items
Merge pull request #531 from Gravatronics/new/emptyTableHandler

Adds a javascript handler for empty tables
Make a little change to the EmptyTableHandler API

Additionally, the default message type is info instead of warning.
Merge pull request #542 from Gravatronics/enhancement/EmptyTableHandler/APIChange

Make a little change to the EmptyTableHandler API
Adds the possibility to auto-trigger action effects in WCF.Clipboard

If a clipboard item has the following parameters:

* actionName
* className
* objectIDs (ids of the marked objects which would be affected by the action)

the following things happen:

* An AJAX action with actionName and className is executed (if additionally a confirm message is given, the user has to handle that first before the action is executed).
* It's checked if an action object for the relevant object type and actionName exists in WCF.Clipboard exists and for each object id in objectIDs triggerEffect(objectID) on the action object is called. This way deleted objects are also removed from the table or toggled objects get updated toggle "buttons".

To achieve the second part, WCF.Action.Delete and WCF.Action.Toggle have a new method: triggerEffect() which is basically the content of _success but can now be called from WCF.Clipboard with the relevant object ids.
Furthermore UserClipboardAction returns the relevant user ids if the delete action is active.

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Additionally, I update the javascript handling of the user list in the acp:

* The deletion button works and uses WCF.Action.Delete.
* The new WCF.Table.EmptyTablerHandler is in use.
* The above mentioned WCF.Clipboard changed are implemented which is mainly adding a few javascript lines and removing several obsolete lines from WCF.ACP.
Fixes ClipboardActionPackageInstallationPlugin

Previously, an actionName has to be unique within a package, now the combination of actionName and actionClassName has to be unique within a package.

Without this fix, you can't install two actions named "delete" within one file - even if they are for a completely different actionClass and page(s).
Merge pull request #544 from Gravatronics/bug/clipboard/PIPFix

Fixes ClipboardActionPackageInstallationPlugin
Merge pull request #543 from Gravatronics/enhancement/clipboard/autoEffectTriggering

Adds the possibility to auto-trigger action effects in WCF.Clipboard
Fixes return value of UserEditor::deleteAll()
Fixes DatabaseObjectEditor::deleteAll() return value

This way the number of deleted objects is returned and not the number of given object ids.
Merge pull request #548 from Gravatronics/bug/userEditorDeleteAllReturnValue

Fixes return value of UserEditor::deleteAll()
Merge pull request #549 from Gravatronics/bug/deleteAllReurnValue

Fixes DatabaseObjectEditor::deleteAll() return value
Added language export function
Merge pull request #551 from Siora/patch-4

Added language export function