Fix sending of Email Reports. Closes #92

[x] I have read the contributing guideline and understand that I have made the correct modifications

Description:

Added sendreports management command as uWSGI daemon in order to fix issues with Email Report feature. A healthchecks.io developer recently confirmed the command is not being started properly by this Docker image. Proper usage of this command can be seen in the official healthchecks docker repository.

Benefits of this PR and context:

Fixes the sending of Email Reports. Closes #92

How Has This Been Tested?

Manually adding the sendreports command to the uWSGI config of an existing installation results in the Email Reports being properly sent out according to frontend user settings.

Source / References:

Self hosted: email summary not working
Official healthchecks.io Docker uWSGI config

linuxserver / docker-healthchecks