Create direct message feature

[ezgisl]

• [x] Create message model including sender, receiver, content and date posted
• [x] Create message list and message create views
• [x] Add message list and message form pages to "Message" section on the homepage
• [x] Add message button to user profiles

[ezgisl]

Direct message model and view committed with "direct message"

[ezgisl]

Message link added to home page and message form modified Pushed to master branch with the commit message "messageform, offerform and profile links updated"

[ezgisl]

UI improvements may be needed for the message section. It will be considered as another issue.