Add constraint to InstanceUser to prevent duplicates

Also adds a data migration to remove any duplicates that snuck in.
Users should only have one InstanceUser per Instance.
Merge pull request #1509 from maurizi/fix-duplicate-instanceusers

Add constraint to InstanceUser to prevent duplicates
Update prototype directory and clean out old files
Add modeling page to prototypes
Continue styling/building simulation modeling prototypes
More modeling edits, styling and structure
Add masks, style layers and panel groups
Finish styling priority layers, add map options
Merge pull request #1528 from OpenTreeMap/release

Merge Release into master
Fix merge error
Fix merge error
update readme intro text
remove extra newline
incorporate @steventlamb's comment
Merge pull request #1529 from andrewbt/topic/readme-update

update readme intro text
Merge pull request #1527 from mtedeschi/topic/sim-modeling-prototypes

Sim/modeling prototypes
Fix incorrect usage of 'is'
Merge pull request #1525 from steventlamb/topic/fix_is_usages

Remove incorrect usage of 'is'
Make OTM1UserRelic inherit from abstract
Miscellaneous Improvements

Add better error message
Rename inappropriately named function
Rename vars with 'hash' -> 'dict'