Allow adding arbitrary properties to OutputPage

Helps to pass extension-specific data

Change-Id: Iea98510abc100128733361f2d2287802f35bb359
[FileRepo] Changed LocalFile locking to avoid breaking transactions.

* Only BEGIN on lock() if no trx was in progress.
  Likewise, only COMMIT in unlock() if the lock() call started a trx.
* This can avoid problems with commiting page update transactions
  prematurely, which could leave broken page stub rows. (bug 40178)

Change-Id: I9a0adb25ee107df9a6bf70c6103ddfb7f034be25
Merge "Allow adding arbitrary properties to OutputPage"
Merge "[FileRepo] Changed LocalFile locking to avoid breaking transactions."