Missing html_entity_decode() for plaintext emails

When Events Manager sends plaintext emails, it forgets to run html_entity_decode() for the body of the message. For example the #_EVENTNAME placeholder may get replaced with Food & #038; Drink Event, minus the space added here because WP forums are too aggressive in HTML entity conversion. What it should be replaced with is Food & Drink Event.

Steps to repeat

1. Have plaintext as the email sending format
2. Add a new event with & in its title
3. Read the event name in the Published Event notification email

This applies to location names as well. Both are fixed by running the email body through html_entity_decode() before sending it plaintext.