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This adds a new tab to the admin window, containing functions for
writing, storing and executing SQL queries. But also, and this is the
big part PRINTING THEM!

The database needs to be patched, see diff.sql.

Currently it pops up a preview dialog, which is good enough for the time
being.

Imported under licence specified in tableprinter.{cpp,h}.

Adds a new table to the database.

Also made the `accTransferText` a QPlainTextEdit instead of a QLineEdit.

This commit introduces a new view in the database

Contains an almost finished GUI (for the money accounts), which probably
won't change. Along with code to popuplate the combo boxes, and the
account list.

Introduces a new view in the DB.

Patch file only for updating. Shouldn't clutter file system after that.

This commit replaces how the diff system for products works under the
hood. The final saved diffs are the exact same as before, and the GUI
has simple received a "quick mode" checkbox.

The major update is that the temp diff table stores a lot less data,
and is accessable as a view, allowing for much easier subquerying in it.

This was also the (I think) last place the database didn't operate on
it's own, but was rather dependent on the GUI. Which makes this really
nice.

==== INSTALLATION ====

Apply the changes in diff.sql to the already existing database, which
creates all new tables, and sets the required data. Note that it doesn't
clean up the old tables. I will probably fix that in the future.