Always close script linemap file after reading and always dispose of other streams in the script engine even if exceptions are thrown.
minor: improve logged error in XEngine.SetXmlState if there was a problem writing the linemap.

The previous error report of already exists is inaccurate since existing files do get overwritten.
Reintroduce general xengine extra debugging log level.  This can be controlled at runtime with the command "debug xengine log <level>", as with similar commands.

If log level is 1 then every script load is logged.
This means the <logger name="OpenSim.Region.ScriptEngine.XEngine"> section in OpenSim.exe.config is no longer needed to avoid log spam on regions with many scripts and can be removed.
minor: If we are recompiling scripts in response to a ScriptStopStrategy config change (a rare situation), then explicitly log this for debug purposes.
minor: Just have one message that displays successful registration of a region with its parameters rather than 2
Remove long unused region parameters from SceneBase.  Some of these weren't even being set.  Region parameters come from Scene.RegionInfo instead.
Don't worry about checking FlotsamAssetCache.m_CurrentlyWriting when updating access time.

The majority of updates won't be for anything currently writing and any sharing exception from an actual clash can be caught and ignored anyway.
refactor: breakout flotasm cache last file access time to separate UpdateFileLastAccessTime() method for imminent reuse.
If "fcache assets" is executed, don't stop with an exception if there's an access violation if another thread is operating on the file at the same time.

Resolves one issue from http://opensimulator.org/mantis/view.php?id=7271
Merge pull request #12 from opensim/master

Merge in commits from opensim master