Papaya-Locking optimizations

[SaschaKersken]

I have reviewed the locking system and in my opinion there are some points to optimize locking without loosing existing functionality but getting a great plus with just a little effort.

• lockTypes: you should reserve a range of lock types for the papaya system to avoid side effects on later extensions
• It is not possible to lock multiple elements. Working in several tabs is state of the art. A variable for the locking mode (single [default] or multiple) and minor modifications of the method setLock should work.
• There is a need for a method to capture an existing lock. Security queries are the realm of the environment and don't need to be implemented in this class.
• On logout all existing locks of the given session should be killed. (Are there any logout hooks at all ?)
• With multiple locks you need a method to remove a single lock and probably a method to get a list of existing locks (by session and optionally by type).

[SaschaKersken]

There is also no chance to get the locking timestamp. It could be important for a concurrent user to know how long a lock is used or at what time the lock was set.