Sc 107/default extention file selection

What's new:

• Automatically goes to the correct dir, depending if you look for shadows or source files!
• Has .csv as default instead of .txt
• Added .TextGrid as option
• Title of file selection window dependent on whether you look for source or shadow files
• File selection function has no code duplication anymore
• Layout of code in some other files is fixed to meet PEP standards

mvc/controller.py

@@ -76,7 +76,7 @@ class ControllerClass:
 
         file_paths = askopenfilenames(
             initialdir=datapath,  # If not found, then not a problem.
-            title="",
+            title="Select " + file_type + " files",
             defaultextension='.csv',
             filetypes=(("Comma-separated values", "*.csv"),
                        ("TextGrid", "*.TextGrid"),