Database changes

The following are expected changes we'll have to make in upcoming versions. It's helpful to keep a note of them so we can do them in one go, as database upgrades in Moodle are a big old PITA.

sloodle_users

1. grid - the grid the avatar is on
2. hypergrid_uuid
3. display_name - the latest detected display name of the avatar

sloodle_layout

1. change key on name to name+controller

sloodle_active_object

1. grid
2. scale

sloodle_currency_types

Added in Avatar Classroom feature branch "feature-currency-upgrade" as 2012121907

1. code - A code to use to match up currencies when importing from backups.
2. is_shown_to_students - Whether the currency should be displayed in the student's backpack etc or just used behind the scenes.
3. is_grid_currency - Whether the currency should be used as the in-world currency for the grid (if we build OpenSim money module integration)
4. scope - round | controller | course | site - How finely-grained the currency handling should be, ie do you get new points for each round, or do your points persist over rounds?
5. classification - money | points | inventory | statistic - The type of currency
6. related_prim_name - the name of an in-world object that is related to this currency
7. max_amount - the highest amount of this currency you can have or 0 for infinite
8. min_amount - the lowest amount of this currency you can have