Reducing install guide build warnings

Limiting the number of words per line in the install
guide and common content to reduce install
guide build  warnings concerning overflow from about 22 to 16

Change-Id: Iac4c5d429e2e35148e98885c180990f90cf9ca15
backport: juno
Closes-bug: #1273143
(cherry picked from commit e9fd4001938b6484c84ff4a53d8c8e5e5ca396ca)