Auto Sort labels bug and other label handling issues

[boutinb]

This solves several issues:

• The "Auto Sort Label per value" setting (true per default in the preferences) is not saved in the database. Now this setting is saved in the database and thus also in the JASP file.
• The "Auto Sort Label per value" works also for non numeric values. Now the labels are per default also alphabetically ordered.
• The Variable Window does not show always the selected column, especially when navigating in the Data view with the keyboard: the Variable Window was showing still the old selected column.
• The up/down/reverse buttons were not visible or/and enabled in the right way. Now if Auto Sort is on, all the other buttons are removed, except the 'Reverse order of all numerical values' if at least 2 labels have numerical values. If Auto Sort is off, all other buttons are displayed, and are enabled only if they really can change the order (the up button is disabled for example if the the selected row is the first one).