Export perm added to UI!

Code added, Along with all the potential PERM_EXPORT bits...
Actual PERM_EXPORT bit still needs to be added.
SimulatorFeature comes next.
Enter PERM_EXPORT, stage right.
Compile fixes.. I thought I'd done this...
Bits and pieces

Disable next owner perms boxes when PERM_EXPORT
Added checks disabling the export toggle conditionally.
All cases covered except textures, couldn't figure that one out...
Mind the TODO's in the diff..
Check if objects textures prevent it from being exportable.
Space changes.
Permissions corrections.
Add Allow exportation checkbox to Default Upload Permissions floater.

Setting is per account and defaults to false.
Clean up in llpanelpermissions.cpp
Space changes
Bit more cleanup in llpanelpermissions.cpp
Such a silly mistake it's "checkbox allow export" not "checkbox export"
Added simSupportsExport function

Hide E and export checked from regions without export support
No longer allow PERM_EXPORT from being added to default everyone permission flags if it's not supported by the sim.
Space changes
Fix debug permissions display to show the transfer permission again.
Fix export enable controls
Fix export permission checks to look for face textures by asset ID
Added handleVisibilityChange to LLPanelPermissions

TODO: Find out if this change is worthwhile by checking for log spam
Condensed export mask checks into boolean functions

Thins out that overly thick block of checks in the middle of LLPanelPermissions::refresh
Also corrected incorrect log output, after First stage comes contents not textures, Melanie.
commitCallbacks have the new value built in, let's not bother with childGetValue for the export check =^*^=