WelcomeScreen: Completely work with ids to switch creation steps.
WelcomeScreen: Place logo with CSS. Fix double click event.

 * Use CSS definition to place logo to easily add additional UI elements at
   the same place (e.g. buttons etc.).
 * Open project with button release not already press event.
Extend symbolsig_to_string (no failures with all vapis).

 * No failures with currently supported symbols (methods and classes). Full
   coverage of distributed vapis for those symbols.

 NOTE: Though the symbolsig_to_string method (and submethods) becomes
       difficult to maintain for different (atm 3) outputs (and we support
       currently only a limited subset of symbols) a small AST (per symbol)
       could be a scalable solution.
       A small parser can then format the symbol's AST representation with
       markup etc.