Large list of bugfixes, probably one more beta release and then RC1

Changes since 8.x-1.0-alpha2:

• by joachim: Fixed mail message entities not declaring their dependency on the message processor plugin provider.
• #2780505 by chaitanya17: Removed obsolete @file tag docblock from all the class files.

There is now an Address form element that can be used in places where there's no configurable field:

Additional features included as below:
1) Using profile image as icon for my-account menu
2) Bootstrap theme compatibility
3) Login logout and my account text configuration from admin settings
4) Some of code fixes and redirect issues.