Remember the symmetry mode in the Constructor between sessions

[sadmoody]

Description: The default symmetry mode is "rotational" - which is absolutely the best default. But you can change the symmetry mode through the settings. Once you do, everything works as intended. However, the setting is not saved between sessions - if you navigate away from the constructor and come back, the symmetry mode will revert to rotational.

Result: This can have a negative impact on people constructing crosswords with a different structure than the default since adding or removing black boxes will make others appear/disappear in unexpected ways if the user assumes they're in a different symmetry mode.

Expected Behaviour: Changes to the symmetry mode are stored in memory and will be automatically set between different constructor sessions.