Improve command aliasing

[fmbenhassine]

As of v3.4, creating an alias for a command is done as follows:

CommandRegistration commandRegistration() {
	return CommandRegistration.builder()
		.command("mycommand")
		// define alias as myalias
		.withAlias()
			.command("myalias")
			.and()
		// define alias as myalias1 and myalias2
		.withAlias()
			.command("myalias1", "myalias2")
			.and()
		.build();
}

The DSL methods command("alias").and() are repetitive. I suggest to shorten them as follows:

CommandRegistration commandRegistration() {
	return CommandRegistration.builder()
		.command("mycommand")
		// define a single alias
		.withAlias("myalias")
		// or define multiple ones at once
		.withAlias("myalias1", "myalias2")
		.build();
}

[fmbenhassine]

Might be related to #1127