Adjust cap required to see About screen

install_plugins lets users activating BuddyPress on a single site in a
multisite see these screens; manage_options doesn’t (that’d be a
superadmin in this case).
Revert "Adjust cap required to see About screen"

This reverts commit 0e5f195191e731085e58d2e79f44f0f20cbabf41.
Add a Dashboard link to the plugin settings area.

Some tweaks to i18n functions, too.
Create a "get" method for bp_core_admin_tabs
Add wrapper element around about screen text