Revert "Changed DocumentCollection's init to check if its provided parent is an AgentContext and, if so, use the context Database instead (Issue #60)"

This reverts commit 3041539fa163b07a282a283990ad38e1cf6101c4.
Revert "Revert "Changed DocumentCollection's init to check if its provided parent is an AgentContext and, if so, use the context Database instead (Issue #60)""

This reverts commit a22eb69f059880687d102416069c0570bb27dc1a.
Moved "addColumn" and "addField" back out of the list implementations
and into the AbstractFolder and DesignForm classes. Also changed the
list classes to be live views on their parents