[FIX] Output file naming and linking problems

[jpfeuffer]

• Auto linking of outfile names for single output ports also considers (as fallback) multifile ports with the first file as basename.
• Removed suffixes since they elongate filenames more and more (and the file can be distinguished by the node-specific folder it is saved in). Thinking about allowing suffixes if the user wants.
• Fixed output folder node such that it appends a number, if the same file basename is encountered multiple times.
• Fixed OutputTypes UI where it would need at least two input ports to start showing the selection of auto (with the new auto linking it shouldnt even matter anymore since everything should be considered).