admin blast - UI adjustments

Tuned the user interface on the blast tool to make it more user
friendly.  Combined the macro editor and the message editor and made the
partition-specific settings easier to find.
admin setup - change plugins to integrations
integrations - add help to Amazon SES
admin - move help

The online doc search is now stacked in the support interface, above the
tickets.
Help is removed from the header.
admin - move downloads link

Downloads was moved from the header to the setup > vstore panel.