Allow team leaders / assistant team leaders to send message to team

[sanderpotjer]

Make a message form for team leaders and assistant team leaders to send a message to the entire team, automatically sending the email to all active team members of a team.

Could be a new tab in the team page, or a new menu item that automatically lists the teams a user (-assistant- team leader) can send a message to.

[sanderpotjer]

Request from the JOD meeting:

• allow volunteers to add multiple email addresses (like personal and @community.joomla.org)
• allow team leaders to select where to send the message to