Add tags for Spring Boot support.

[mrglavas]

• Adding tags for springBoot1 and springBoot2.
• Updated README with information on new tags.

[mrglavas]

@NottyCode you'll notice copies of server.xml in each of the sub directories. I would have used templates for springBoot1 and springBoot2 but I understand that they don't exist.

@dazavala has tested the new images and they work as expected.

[dazavala]

@NottyCode What a coincidence. Earlier today @tjwatson and I discussed the lack of a server template for springBoot images. Our take is that we want them in the next release. Agree?

@arthurdm I've drafted the springBoot updates to the docker hub websphere-liberty image readme that discusses image content and usage (https://github.com/docker-library/docs/tree/master/websphere-liberty). Hopefully I can connect with you or @mrglavas today before 3:00 cst.

[NottyCode]

@dazavala I agree we should have had the springboot 1 and 2 server templates. We should get that fixed in the next release.

I've taken a local copy of the changes and I've run them through bashbrew and it looks like it all builds. I think the OpenJ9 Docker images aren't where they need to be, but a) none of them are and b) we haven't published them and until we do I don't think there is much need to worry about any possibly tidy up now.