Update suggested version of MySQL from 5.6 to 5.7
Update suggested version of MySQL from 5.6 to 5.7

The install commands suggested MySQL 5.6. Following this suggestion
caused me errors when installing on Ubuntu 16.04, as the package could
not be found. We don't have a reason to stipulate MySQL 5.6, so this
updates the install command to suggest 5.7, which worked.

Task: 3231

Change-Id: I122b99df68d3866ac8aa6ce5ca8709a0adeaeef4

ColdrickSotK/storyboard,ColdrickSotK/storyboard,ColdrickSotK/storyboard