Merged RelUndoAction and UndoAction from x2b:5ad37d
Fixed typo

Signed-off-by: Wilson Brenna <wbrenna@uwaterloo.ca>
Fixed scaling undo

The EditSelection used to create a ScaleUndoAction
and a MoveUndoAction after scaling the content
in certain ways.

Signed-off-by: Wilson Brenna <wbrenna@uwaterloo.ca>
Make XInput fix optional

The XInput issue was fixed in gtk some versions back.
The fix provided by Xournal++ does in this case have
the opposite effect of breaking everything. The fix
can now be enabled / disabled from the settings dialog
without having to recompile the code.

Signed-off-by: Wilson Brenna <wbrenna@uwaterloo.ca>
Improved scaling of Strokes

The thickness of strokes used to be scaled by
a factor of (fx + fy)/2 for scaling factors fx, fy > 0.
This has the disadvantage that for fx != fy undoing the
scaling operation does not restore the correct thickness,
since (fx + fy) != 1/(1/fx + 1/fy) in general. Using the
geometric mean of fx and fy instead of the arithmetic mean
seems to be a better choice.

Signed-off-by: Wilson Brenna <wbrenna@uwaterloo.ca>
Fixed some glade warnings

Warnings issued previously:

"libglade-WARNING **: unknown attribute `swapped' for <signal>."

This thread suggests that the "swapped" attribute is some legacy
property and can be removed.

http://stackoverflow.com/questions/7827310/how-do-i-fix-the-unknown-attribute-swapped-warnings-from-libglade

This appaerently gets rid of the warning without any side effects

Signed-off-by: Wilson Brenna <wbrenna@uwaterloo.ca>