Enable a small set of apps and openoutreach_front_page when installing with Drush / Aegir

Problem/Motivation

As of #1815944: Don't enable apps by default when installing from Drush, when Open Outreach is installed with no apps enabled and only the openoutreach_core feature enabled.

While we made this change intentionally, the result may cause difficulty or confusion for new users, for whom the site may appear broken or, at least, they may find it difficult to know how to proceed.

Proposed resolution

• Determine a limited subset of Apps to enable when installing via Drush / Aegir. Without user input to select which to enable by default, we should be conservative and select only a small subset, rather than all those that are preselected by default in an interactive install.
• Alter the openoutreach_front_page callback to enable if installed via Drush.

Remaining tasks

Specify subset of apps to be enabled in Drush install.