+ add signal showFormulaDialog to QuantitySpinBox in order to indicate whether the formula dialog opens or closes
+ when formula dialog opens then hide the button box in the parent dialog, show it again when the formula dialog closes
- basic infrastructure for handling of expressions
- port the unit properties editor to support expressions
- port placement editor to support expressions
- expressions for double spinbox
- expressions in sketch constraints
+ set application-wide event filter and handle mouse press events
+ fix expressPosition() to return exact position of line edit
+ fix warnings in ui file
+ use DlgExpressionInput as non-modal dialog in QuantitySpinBox