Allow messages to be sent to other users

[hellboy1975]

I'd like to move away from having the email addresses of users visible to other members. To allow users to talk though, I'd like to replace this with a simple messaging system, that allows one user to message another.

Requirements:

• When a message is received, it should show a notification to the recipient in their dashboard
• Users should be able to disable the ability to be sent messages

Out of scope but should be considered when designing:

• Users could opt to have an email sent to them when recieving a message
• Consider an option to send messages to a group of people
  • How many people is a suitable max? 10?
• As an anti spam measure, users should be limited to how many messages they can send in a period of time
• Could include a recaptcha on the sending mechanism?