Needless re-writing of config data

[skandragon]

When importing a lot of books, I saw the dedrm.json file be re-written each time a book was processed. The content did not change. For a flash drive, this hurts with huge collections.

[apprenticeharper]

Thanks for the report. This isn't a high priority for me, but if someone submits a pull request with a fix, I'll probably include it.

[skandragon]

It's a big deal for those of us on SSDs. I may try to dig into the code later.

[apprenticeharper]

I took a look at this, but the preferences code is rather complex, relying on calibre for writing the preferences out. I am still looking at this on and off, but if anyone has some suggestions, I'd be pleased to hear them.