Fixed issue #333 "Writing to files with non-standard extension is not possible"
Fixed issue #332 "The 'floor()' function is not working on data sets"
Fixed issue in implementation of #326 Changed the vector name creation method for the multi-argument methods
Fixed issue #330 "Files still cannot be saved in some cases"
Fixed issue in implementation of #326 Multi-argument functions are now only replaced, if they are surrounded by parentheses from both sides.
Fixed issue #329 "'interpolate' masks 'steps' in plots"
Fixed issue #328 "Cache headlines disappear after deleting part of the cache"
Fixed issue #327 "Comment sequences in strings are interpreted wrong"
Fixed issue in implementation of #326 Improved parentheses handling
Fixed issue in implementation of #326 Added check for strings