BF: when Text or TextBox had default of "" the script contained "''"

This looks like it was a long-standing bug never notixed because in Text
nobody ever creates blank text this way. This was copied across to TextBox
where the issue became more obvious.

Author: peircej

psychopy/experiment/components/text/__init__.py

@@ -147,7 +147,7 @@ def writeInitCodeJS(self, buff):
             if inits[param] in [None, 'None', '']:
                 inits[param].val = 'undefined'
                 if param == 'text':
-                    inits[param].val = "''"
+                    inits[param].val = ""
 
         code = ("%(name)s = new visual.TextStim({\n"
                 "  win: psychoJS.window,\n"

psychopy/experiment/components/textbox/__init__.py

@@ -238,7 +238,7 @@ def writeInitCodeJS(self, buff):
             if inits[param] in [None, 'None', '']:
                 inits[param].val = 'undefined'
                 if param == 'text':
-                    inits[param].val = "''"
+                    inits[param].val = ""
 
         code = ("%(name)s = new visual.TextBox({\n"
                 "  win: psychoJS.window,\n"

psychopy/experiment/params.py

@@ -152,7 +152,7 @@ def __str__(self):
                 return "%i" % self.val  # int and float -> str(int)
             except TypeError:
                 return "{}".format(self.val)  # try array of float instead?
-        elif self.valType in ['extendedStr','str']:
+        elif self.valType in ['extendedStr', 'str']:
             # at least 1 non-escaped '$' anywhere --> code wanted
             # return str if code wanted
             # return repr if str wanted; this neatly handles "it's" and 'He