Add new column 'public_avatar_p' to the 'user_preferences' table, in order to allow the user to decide wheter to make the avatar (profile picture) public to other users or not, with a conservative default, false. Add also a simple API to get/set that value and bump acs-kernel version number.
Moved "bio" back to "person", but with type-specific storage. People can fight over where such things belong on another day, for now keeping it in "person" has the advantage that the Tcl API is 100% unchanged so moving it to type-specific storage won't break .LRN.