EssentialsX Selectors: @a, @p, @r (Addon)

This release adds full support for vanilla parity for command selectors! This now means that any (player) selector or specification that's possible in a vanilla command now works for essentials commands as well. (Note this does not include @n or @e, as Essentials commands are fundamentally incompatible with such selectors.)

• Fixes #17 (hopefully)
• Implements #16

Unfortunately, the code under the hood for this plugin is still pretty rough overall, and unfortunately there is still no tab completion for the selectors, but I hope to address both of these issues down the line.

Thank you to xgioa, wrjgrrgpmc-hash, and hellfirehd for their reporting and feedback!