Collections Demo App + Tutorial

[yknl]

• Support for multiple identities on collections
• File Rename and Status

[moxiegirl]

@yknl This should be in the documentation not in the blockstack.js library. Any objections to moving this issue to docs.blockstack.org?

[yknl]

sounds good 👍

[moxiegirl]

@yknl As discussed we should be working to add collections functionality to StackIt that @Sahana-Srinivasan wrote.