I want to name assessment tray configs

[adaburrows]

Instead of associating an assessment tray with a specific resource definition, we want the assessment tray configuration to have a name. Also, we should allow choosing a default config for each resource def.

• We need to change the whole structure of how assessment trays are stored:
• • [x] Instead of having links that point from the resource def eh to the assessment config blocks, we should have a separate assessment tray config objects with names.
• • • [x] It should have the name of the tray.
• • • [x] This should contain the assessment blocks in a vec.
• • [x] The current code that creates links to the config blocks can be modified to point to the assessment tray config object.
• [x] Change the current page to remove the list of resource defs from the side panel.
• [x] Add a list of named and saved assessment trays.
• [x] Add a button above the list to add a new assessment tray.
• [x] Keep the current controls for adding and editing assessment trays the same, but add a field at the top to name the currently selected assessment tray.
• [x] Add one page that list all the resource defs and lets people choose assessment trays from a drop down list in order to configure defaults.

[adaburrows]

Note, this relates to #190. This means we don't have any of the UX thought out yet, but we can still get the code in place for it.

We will still need to:

• design how the actual UX will unfold for this screen
• design the UX around how the user will select the assessment tray when making a post
• the code interface that lets us store the user's choice