Feature request: set tag of files in UI

[SpiritSuperUser]

So far, only the config file can be used to set the tag which is used for the file names. It would be useful to set this withing the UI as well.

[GPMueller]

Since commit ad9c9d4c65044c1e062dc8bd192f71fa3b457a52 the ImGUI app is available on the develop branch, and since commit 728b47800b5f1e5f50a0a4b0015a115d9b291226 it arguably works quite well. The "File" -> "settings" menu of the new app could hold settings for

• the output file tag
• the log file directory
• console and file log levels
• whether to write a log file or output to the console

The config also provides "initial" and "final" saving of config-file, spin positions and neighbours. I think it would make sense to have buttons to output each of them as they currently are, but I don't think that belongs into the settings menu...