Add query modifier for checking acting player info

[Pugzy]

Let's say you wanted to prevent a player from opening chests unless they're in a specific region (the wool room maybe).

The current way of filtering location on a block-break or use event target the location of the physical block (which is always in the wool room). In this instance, I want to query the location of the actor (player) rather than the block in question.

For this, I have created a PlayerBlockQueryModifier which sets focus on the player in the event vs the block. This also slightly modifies the newly created base QueryModifier class allowing for unmodified queries to abstain by returning null. In this case, the player within the PlayerQuery can be null (when offline) so a fallback was required.

See the example below where the player can only use items within the yellow wool room if they too are in that region.

<!--- filter with region -->
<player id="player-in-yellow-wool">
    <rectangle id="yellow-wool-room" min="534.5,-354" max="544,-339"/>
</player>

<!--- application -->
<apply use="player-in-yellow-wool" region="yellow-wool-room" message="You can not interact with this from here."/>

Open to suggestions if this can be completed an alternative way (existing XML or improved implementation).
Discussed with Pablo and Simon in Discord so ty for help.

[Electroid]

Awesome! Excited to see the use-cases