Use FastSchematicReader by default

[SirYwell]

Overview

Description

HashMultiMap has no guarantees about the order of the values for a key. In our case, this leads to SPONGE_SCHEMATIC being first when iterating in ClipboardFormats.findByExtension(...). We want FAST to come before, therefore we should use a MultiMap where values are in the order they are registered. This matches the registeredFormats list used by findByFile.

The change to the command is needed to allow actually enforcing a different schematic format.

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