Pdfebc-core

Some major improvements in this release!

Enhancements

* `compress.compress_multiple_pdfs` is now a generator 278738e549bdd38a11ad49aaff64e0168351e440
* Callback functions for status messages has been removed. Some status messages are now logged instead, and some have been removed (responsibility moved to the UI instead) 278738e549bdd38a11ad49aaff64e0168351e440
* `smtplib` replaced with `aiosmtplib`, for asynchronously sending emails f943b09f7bd1d3fd7e0b69f6c21057a20e3e3659 (enables the cli to have an animation running when sending emails, among other things)

Change log:

* 100% test coverage bdadc9e31b05afd5ebb23b5ec48fe497b18d5a36
* `utils.py` refactored into three separate modules (`email_utils.py`, `config_utils.py` and `misc_utils.py`) 84ecf7fc9f3424bab2478b1d8f26be711b30c757
* Reworked api 57f9827387e001dfe1224bcdc0494938991b7559

All planned functionality of `pdfebc-core` is implemented. The API is however messy and has little thought behind it, as it originally was not meant to be a standalone package.