Zimscraperlib

- added UTF8 to constants
- added mime_type discovery via magic (filesystem)
- Added types: mime types guessing from file names
- Revamped zim API
- Removed ZimInfo which role was tu hold metadata for zimwriterfs call
- Removed calling zimwriterfs binary but kept function name
- Added zim.filesystem: zimwriterfs-like creation from a build folder
- Added zim.creator: create files by manually adding each article
- Added zim.rewriting: tools to rewrite links/urls in HTML/CSS
- add timeout and retries to save_file() and make it return headers

- fixed `convert_image()` which tried to use a closed file

- exposed reencode, Config and get_media_info in zimscraperlib.video
- added save_image() and convert_image() in zimscraperlib.imaging
- added support for upscaling in resize_image() via allow_upscaling
- resize_image() now supports params given by user and preservs image colorspace
- fixed tests for zimscraperlib.imaging

- added video module with reencode, presets, config builder and video file probing
- `make_zim_file()` accepts extra kwargs for zimwriterfs

- added translation support to i18n

- added s3transfer to verbose dependencies list
- changed default log format to include module name