server_dev.parameters: add back option to browse remote tada servers in developtment mode

Useful for testing on a tablet etc.
Fixed Dialog.Rebase and Dialog.WelcomeMessage to match new start() and startWithoutExpression() behaviour (refs agmen-hu/consoloid-console#6)

WelcomeMessage: Removed all code related to not dealing with non existent expression.
Rebase: simply calls startWithoutExpression() insetead of calling setup and render manually. (Also why was setup given those arguments? Rebase#setup() does not exist. AbstractDialog#setup() does not need them.)