Conditionalize capability trimming content specific to EAP XP

We were asked to make several updates in the shared capability trimming content to add content for EAP XP.  We should conditionalize this content so it appears in the XP documentation, and does not appear in the OpenShift documentation.

Examples include:

• the content is in the "using MicroProfile...." book, so definitely OpenShift oriented but the initial section should have a link to the bootable JAR chapter IMO.
•  Building custom layers for JBoss EAP -> 3. In the pom.xml file used to build your custom feature pack, refer.., here the galleon pack version (7.3.0.GA-redhat-00004) could be updated to a more recent one. BTW I think this should just be wildfly-galleon-pack and that's it, so that the following note is removed to, because this is the XP 2 book.
• I checked with Darragh to confirm that user-developed custom layers are not supported for the bootable JAR. I added a Note describing this limitation to the module on provisioning user-developed layers.
• In "Building custom layers, the values of the <artifactId> and <value> attributes in the example pom.xml file in step 3.