Changed table 'im_offline' to use UTF8 characters. This fixes a problem with Offline IM V2 (only relevant to MySQL).

This fixes http://opensimulator.org/mantis/view.php?id=7123

Users that use MySQL should change their MySQL configuration to support UTF8. In the config file /etc/my.cnf (Linux) or my.ini (Windows), add these settings:

   [mysqld]
   character-set-server=utf8

   [client]
   default-character-set=utf8

And then restart MySQL (on Linux: "sudo service mysqld restart").
Workaround for SRAS: if Store Asset returns 'null' then assume the asset already exists, and this isn't an error
Eliminated many warnings
Eliminated 'Obsolete' warning: don't call do-nothing function SetPreviousAppearance()
Removed GetUserInventory(). It wasn't being used, and was creating warnings because it's Obsolete.
Removed references to Community.CsharpSqlite*.dll. This eliminates some warnings, and SQLite still works.
Hypergrid: don't send Local assets to other grids

This commit also contains other changes, but they're all just for clarity. The only actual behavior change is to avoid Posting local assets.
Dynamic textures shouldn't be saved in the assets service (only in the simulator cache)