Quitting the "Do you wish to save your changes" file explorer prompt quits the program, instead of quitting the file explorer

[Nevo magnezi]

Sometimes people accidentally click "cancel" instead of "save."

In my experience, redirecting to the "would you like to save your changes" pop-up is a more conservative approach to a user's wishes and ensures that they really do intend to quit without saving.

[Siddharth Shekar]

Fixes #36

→ <<cset 545f72cb7bc5>>

[Nevo magnezi]

Unfortunately, the symbols added to the schematic disappear after I tested this:

Placed symbol -> quit -> clicked save -> clicked cancel -> symbol disappeared after several seconds

I'll attach a log file.

[Siddharth Shekar]

Fixes #36

→ <<cset 124345c4cbee>>

[Siddharth Shekar]

This was happening because I prepare for saving because actually getting a valid file name and didn't tear down the preparations I had made properly. In the latest commit, I've moved the prepping part to after I get a valid file name so no tearing down is necessary.