replace CDX 1.5 deprecated tool

[hboutemy]

fixes #487

for CDX 1.5+, generate:

<bom xmlns="http://cyclonedx.org/schema/bom/1.5">
  <metadata>
    <tools>
      <components>
        <component type="library">
          <author>OWASP Foundation</author>
          <group>org.cyclonedx</group>
          <name>cyclonedx-maven-plugin</name>
          <version>2.8.1-SNAPSHOT</version>
          <description>CycloneDX Maven plugin</description>
          <hashes>
...
          </hashes>
        </component>
      </components>
    </tools>
...

instead of

<bom xmlns="http://cyclonedx.org/schema/bom/1.4">
  <metadata>
    <tools>
      <tool>
        <vendor>OWASP Foundation</vendor>
        <name>CycloneDX Maven plugin</name>
        <version>2.8.1-SNAPSHOT</version>
        <hashes>
...
        </hashes>
      </tool>
    </tools>
...