Removing locking on requests in MySQLAssetData.

These locks are not necessary since the connection is taken from the underlying mysql pool and not shared.
Such locking is already not done by some other parts of OpenSim.Data.MySQL.
Pointed out by arribasim-dev
Remove lock in MySQLFramework.  This is not necessary as the connection is not shared.
Remove some use of database connection locking from MySQLSimulationData - this has not been necessary for some time as database connections are not shared.

However, many locks remain since they may effectively be providing transactionality in some operations (e.g. prim updates across multiple tables).
These are candidates for being replaced with proper database transactions, since this would not block unrelated operations (e.g. land save and object save)
or unrelated operations on the same tables (e.g. storage of one linkset whilst another is being removed).
In practice, any performance deg due to contention is probably rare and short lived as the major prim operations are performed in memory and only persisted some time afterwards.
Remove query locking in MySQLUserProfileData.  This is not necessary as the connection is not shared.
Remove database connection locking in MySQLXAssetData.  This is unnecessary as connections aren't shared and transactions are already in place where necessary.
Add back URL endings in examples
Merge branch 'master' into bullet-2.82
Implement experimental non-default mechanism to update scene via a timer rather than a persistent thread with sleep.

This is to see if an inaccuracy in sleep times under load is responsible for increase in frame times even when there is spare time still available.
Can currently only be activated by setting "debug scene set update-on-timer true".
Can be switched between timer and thread with sleep updates whilst the scene is running.
Fix frame times when updating scene on timer.
Remove race conditions from where SP.AbsolutePosition could change between the various property checks.
Don't allow update timer to invoke another scene update if the previous is still active.
On code section that rezzes single objects and attachments, reduce CPU use by reading asset XML a single time with a stream reader rather than multiple times.

Reading large XML documents (e.g. complex attachments) is CPU expensive - this must be done as few times as possible (preferably just once).
Reading these documents into XmlDocument is also more resource intensive than using XmlTextReader, as per Microsoft's own publication "Improve .NET Application Performance and Scalability"
Optimization of other cases will follow if this change is successful.
minor: Eliminate more unnecessary code copying individual parameters for Vector3 copying in Scene - this is not necessary as Vector3 is a value type
Add regression test for deserializing xml objects with more than one non-root part.
Fix recent regression test TestDeserializeXmlObjectWithOtherParts() which was not meant to indent the input xml
Ignore whitespace when reading serialized XML objects.

This was previously effectively being done by XmlDocument in the multiple passes through the XML.
This change tells XmlReader to ignore whitespace.  This also means changing arguments to use XmlReader instead of XmlTextReader (a descendent of XmlReader) directly.
XmlReader.Create() has been the recommend way to create XML readers since .NET 2.0 as per MS SDK and is the only way to specific ignore whitespace settings.
Implement STATUS_BLOCK_GRAB_OBJECT in llSetStatus()/llGetStatus() and correct effect of STATUS_BLOCK_GRAB

As per http://wiki.secondlife.com/wiki/LlSetStatus
Setting STATUS_BLOCK_GRAB_OBJECT prevents or allows move of a physical linkset by grab on any prim.
Setting STATUS_BLOCK_GRAB prevents or allows move of a physical linkset by grab on a particular prim.
Previously, setting STATUS_BLOCK_GRAB would prevent drag via all prims of the linkset.
Fix issue where moving a seated avatar would not adjust their subsequent stand position.

Addresses http://opensimulator.org/mantis/view.php?id=7299
As per the LL grid, for attachments make llGetObjectDetails() OBJECT_ROT return the avatar's rotation.

This is already the behaviour of OBJECT_POS.
Partially satisfies http://opensimulator.org/mantis/view.php?id=7177
minor: fix wrong indentation in previous commit 0cc3cd