v0.9.1

This is a plugin-only release for Focalboard, and is the same as v0.9.1 - RC4.

NOTE: The v0.9 Focalboard plugin requires Mattermost v6.0.

Major updates in this release:

• Workspace switcher and dashboard. Thanks @harshilsharma63 and @asaadmahmood!
• New date range property type. Thanks @sbishel!
• Table calculations. Thanks @harshilsharma63!
• Changed the urls to use routes instead of query parameters. Thanks @jespino!
• Revamped websocket communication layer. Thanks @mgdelacroix!
• Add clear button to value selectors. Thanks @jespino!
• Fix auto-size columns in FireFox. Thanks @kamre!
• Fix comments not appearing in readonly view. Thanks @harshilsharma63!
• Multi-line card titles. Thanks @kamre!
• Add unit tests for sqlstore. Thanks @yedamao!
• Add makefile documentation. Thanks @Szymongib!