Split QSG abstract into multiple paragraphs.

For easier readability and alignment with the other documents, this
patch splits the Quick Start Guide's abstract into multiple paragrahs.

Change-Id: Id644a83dc353f0a17d8e8cbdee9394938823ea8b
Signed-off-by: Jan Hilberath <jan@midokura.com>
Merge "Split QSG abstract into multiple paragraphs."