Allow merging GloomDefinitions with GloomDefinitions, instead of just GloomDefinitions with ClassDefinition

[coderbot16]

Since GloomDefinitions#merge constructs a new Set for each merged ClassDefinition, currently merging two sets of GloomDefinitions together is very inefficient. A proper merge function would be more efficient and clear.

for (ClassDefinition definition : proposedDependencyJar.getGloomDefinitions().getDefinitions()) {
	this.gloomDefs = this.gloomDefs.merge(definition);
}

versus

this.gloomDefs = this.gloomDefs.merge(proposedDependencyJar.getGloomDefinitions());