User Guide: Sandboxing - for Review

Hi Rich,

Here's the Sandboxing content that I edited from Mike Han.

I know there are a lot of images, but didn't know if you wanted to keep them if we're staying web for the 6.2 user guide. I'm not sure when this app is going live. But I've attached an MP description and images to the Jira ticket for the MP team.

Thanks for reviewing!

https://issues.liferay.com/browse/LRDOCS-975