Remove XEngine.m_uniqueScripts

This provides no obvious benefit as far as I can tell but has a definite cost in keep script strings in memory for the entire simulator session.
Adding command to reset user's email address
Add command to reset region's user cache
Fix recent regression where a race condition meant SP.MakeRootAgent() would sometimes look to start attachment scripts before ETM.HandleIncomingSceneObject() had added them.

Probably a regression since ghosts branch merge on Nov 26 2014
In XBakes use proper disposal semantics to always close the stream on Store() no matter what
Use using() semantics in XBakesModule to ensure disposable objects are alway disposed no matter what
minor: Correct propery doc RestClient._resource spelling mistake
In XBakesModule.Get() use using() to always dispose of RestClient which disposes the stream rather than disposing the stream directly
Make sure we always dispose of disposables inside RestClient.Request()
BulletSim: code for lock linear and angular axis ExtendedPhysics
BulletSim: pass access lock parameters correctly. Don't offset linear limits by the object position. Limits are all object relative. Add axis limit locking and unlocking for all axis of a type (lock all linear, ...).
BulletSim: move axis lock constraint addition to pre-step time so constraint is not disabled by a compound linkset rebuilding. Add invocations of UpdatePhysicalProperties() to operations that create movement actors. Previously, the actor could go un-initialized until its Refresh() is called which might never happen.
BulletSim: check for rebuilding in progress when changing linkset position while a linkset is being constructed. This fixes a crash that can happen when complex linksets are physical when a region is started.
Merge branch 'axislock1' of github.com:Misterblue/opensim into axislock1