This addresses and hopefully fixes the bug present in #13

Thanks to @ardse for reporting!

## The entire plugin has been rewritten from scratch!

### What does this change?
- Much more maintainable back end, way easier to contribute as well
- Updates will be quicker, bug fixes will be easier and faster
- The system is way more modular: there is very little hard-coding and bad practices (which is just better for everyone)
- More efficient; the tiniest little bit faster than the previous version, but you won't notice it
### Additions:
- Added the ability to use and (&) and or (|) operators is specifications.
- Example 1: `/kill @a[tag=dog|cat&!rat]` would mean "kill all players with the tag "dog" OR "cat", and they don't have the tag "rat"
- Example 2: `/feed @r[team=red|blue|green,tag=player&!staff,gamemode=!creative&!survival]` would mean "feed all players on team "red" or "blue" or "green", who has the tag "player" and not the tag "player, who's gamemode is not survival or not creative.
- Due to the logic of how it work, you always need to put all of your OR statements before your AND statements, so for example, `/kill @a[tag=red&blue|green]` would NOT work, due to the implementation of this system.

- Fixes # 12

Thanks @moraedu for reporting it!

This will probably be the last 1.x release, as the next version releasing soon will be a full rewrite with more features and better code!

Noticeable changes

• Fixed #11. Thanks to @Skyw0lf07 for reporting it!

Backend Changes

• Refactored project structure a bit
• Switched to using Maven
• Formatted some files better

Allows this resource to be fetchable from the Aternos plugin downloader.

Small update to fix Issue #9. Should also fix any other similar issues

This updates adds a few new features, and fixes some bugs that previously existed!

Additions:
- Added a team specification for selectors, usage is [team=coolTeam] or [team=!green]. (Check documentation on the spigot page for more info). Important note: The team display name is different from the actual name, make sure to use the actual name of the team when using.
- Added support for all plugins in the EssentialsX franchise.

Changed and bug fixes:
- Fixed an issue with the @p selector being used with players in different worlds.
- Changed some default permissions from 'op' to 'true', meaning that every player can use selectors by default.

WOW! The biggest update yet! Big new features!
This update adds specifications for selectors, for example: "@r[gamemode=creative]"

There are 5 specifications that can be added to any selectors:

• gamemode
• tag
• limit
• distance
• level
  You can also add a "!" before a value to do the opposite. For example: "@a[tag=!"CoolTag"]"

For a list of what all of these do, and how to use them, refer to the spigot page documentation HERE.

- Added permissions to all the selectors (Thanks NoPlagiarism)
- Permissions are:
- "essxselectors.use" for using any selectors in general. This is given to all players by default.
- "essxselectors.all" for the "@a" selector. This is given to all players by default.
- "essxselectors.self" for the "@s" selector. This is given to all players by default.
- "essxselectors.random" for the "@r" selector. This is given to all players by default.
- "essxselectors.closest" for the "@p" selector. This is given to all players by default.
- Minor fix.

Changes:

• Added support for all Minecraft versions between 1.8 and 1.18
• Changed compiling version from Java 17 to Java 8

Added a check for the EssentialsX plugin on startup.