show a standard avatar for users, who don't have their own avatar.
Signed-off-by:Thorsten Eurich <thorsten@eurich.de>
helptext for default avatar.
Signed-off-by:Thorsten Eurich <thorsten@eurich.de>
avatar_default should use the self default value for all database types 
Signed-off-by:Thorsten Eurich <thorsten@eurich.de>
added the avatar_default variable to the _dia_ upgrade files.
Signed-off-by:Thorsten Eurich <thorsten@eurich.de>