Download plugins from repositories

[mssalvatore]

Description

The Island should download plugins from the plugin repository instead of including them in the Island package.

Tasks

• Add logic to detect whether or not the Island is a development or release version. Use the development repository if a development version, or the hardcoded release repository if it's not a dev version. Log which repository is being used to make testing simple. - @shreyamalviya
• Modify the jenkins Island build jobs to no longer include the plugins - @shreyamalviya
• Modify BB tests to install the latest version of each available plugins - @shreyamalviya