Restore compression of SVG files on export

[Self-Perfection]

I'm working on shared deck, which is going to contain ~ 280 MB of SVG images. Since 3bbd0bc media files are stored in exported deck without compression and exported .apkg file takes whole 280 MB instead 80 MB that it takes with compression. Huge waste of space.

[coveralls]

Changes Unknown when pulling a5b0852 on Self-Perfection:compress_exported_svg_files into * on dae:master*.

[dae]

Looks good, thanks.

[Self-Perfection]

Probably compression of all exported media files should be restored.

A couple of days ago I stumbled upon shared deck, which contains 373MB of uncompressed jpg and mp3 files but 39% less space in compressed apkg form! Seems mostly due to mp3 files. That is quite surprising.

Assumption that media files can't be deflated considerably might not be true even for non svg files. There is a bunch of real word shared decks that might be used to gather stats and decide whether media should be deflated or not. I propose to run something like

find "$SHARED_DECKS_DIR" -size +1M ! -newermt '2016-02-26' -exec sh -c "unzip -v '{}' | tail -1" \; | sort -rnk3 | nl

and see real numbers to decide. This oneliner finds files over 1MB which were modified before date of commit, which disabled compression, and prints numbered list of stats for each file ordered by space saved percentage

[dae]

If the mp3s are very small then they probably compress well because ID3/standard boilerplate makes up a decent amount of the total size.

The speedup from removing compression was something like 1000%, and in the backup/collection import/export case the space savings are not worth it. But I will think about whether it makes sense to make it available as an option in the future - thank you for the feedback.