Provide a "bom" for Maven Xtext dependencies

I was wondering if we should provide a "bom" for Maven dependencies used in Xtext Maven projects; this should only list dependencies in dependencyManagement section with the versions, and Maven projects could use something like

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.eclipse.xtext</groupId>
            <artifactId>org.eclipse.xtext.maven.bom</artifactId>
            <version>XTEXT VERSION</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

This way, actual dependency versions should not be kept updated throughout all the Maven projects each time a new version is released, but only in the bom.

Not to mention that versions are hardcoded in poms generated by our wizards, like in the .ide project:

	<dependencies>
		<dependency>
			<groupId>log4j</groupId>
			<artifactId>log4j</artifactId>
			<version>1.2.16</version>
		</dependency>
		<dependency>
			<groupId>org.eclipse.lsp4j</groupId>
			<artifactId>org.eclipse.lsp4j</artifactId>
			<version>0.2.1</version>
		</dependency>
		<dependency>
			<groupId>org.ow2.asm</groupId>
			<artifactId>asm</artifactId>
			<version>5.0.1</version>
		</dependency>
		<dependency>
			<groupId>org.ow2.asm</groupId>
			<artifactId>asm-commons</artifactId>
			<version>5.0.1</version>
		</dependency>
		<dependency>
			<groupId>org.ow2.asm</groupId>
			<artifactId>asm-tree</artifactId>
			<version>5.0.1</version>
		</dependency>
	</dependencies>

and using deps from the same groupId forces to repeat the version consistently (like in the ow2.asm above).

The approach of the bom seems to be a success in projects like Spring and Spring Boot, for example.

Start by inspecting the Maven projects and wizard-generated .ide POMs mentioned in the issue, focusing on their dependencyManagement sections and repeated versions. Define the proposed org.eclipse.xtext.maven.bom artifact and verify that consuming projects can import it while centralizing the dependency versions.