[Annotations] Entering a comment for an annotation saves the annotation at each character

[pafonta]

Steps:

1. Create a new annotation.
2. Enter a character in 'Comment'.
3. The annotation is saved.

For an annotation of type 'text':
The dialog Before saving changes to this annotation, you must enter an "Annotated text" and then localize it. appears.

For an annotation of type 'position':
NeuroCurator crashes (v0.4.4 but not v0.4.3 even if the exception is the same) with:

Traceback (most recent call last):
  File "/Users/fonta/repos/neurocurator/neurocurator/annotWidgets.py", line 201, in savingNeeded
    self.updateCurrentAnnotation()
  File "/Users/fonta/repos/neurocurator/neurocurator/annotWidgets.py", line 210, in updateCurrentAnnotation
    self.editAnnotWgt[self.annotationTypesCbo.currentText()].updateCurrentAnnotation()
  File "/Users/fonta/repos/neurocurator/neurocurator/annotWidgets.py", line 533, in updateCurrentAnnotation
    self.container.currentAnnotation.localizer = PositionLocalizer(int(self.noPageTxt.text()), float(self.xTxt.text()), 
ValueError: invalid literal for int() with base 10: ''