Use a common format for all include guards, make sure each header file
has one and make sure it's named after the file name.
And as a random extra in this commit: Make sure the gen_version.h file
generated by cmake ends with a line break.
Closes#59.
Rewrite the dialog to import CSV files using a Qt Creator form file.
Simplify the CSV import a little bit.
A bit unrelated, but needed for this anyway:
Create the restorepoint right after opening a database file instead of
just doing so after the first change.