Update bootstraps with "demo-content" sentances on the demo-project home page for the features in 5.3

Personalization
The Magnolia personalization feature is based on page variants. A variant is alternative content that replaces the original content in personalized delivery. Magnolia serves the variant instead of the original element when personalization rules match.

Tasks in publishing workflow
Starting with Magnolia 5.3, we move from messages to tasks. Tasks have an assignee and status. We display both in the Pulse. When an editor publishes a page, a task is sent to publishers.

Content connector
Typically the content you manage in Magnolia is stored in the JCR repository but it doesn't have to be. With Magnolia 5.3, we decouple content management from the storage location. A new content connector defines where the content is stored.

DAM API rewrite
Magnolia 5.3 introduces an improved DAM API. The rewritten API is simpler and more basic, making it easier to understand and extend. It is also generic in the sense that it is not coupled to the JCR anymore.

PDF and video previews
A new DAM Preview module creates thumbnail previews for PDF and video assets. The thumbnail image displays the first page of a PDF or the first frame of a video, making it easier to choose assets with a quick glance.

Marketing tags
A new Tags Manager app is a central place for managing marketing tags such as Web analytics, third-party content and advertising network code snippets. The app allows you to create tags and place them on pages.