Remove Oracle JDK support

[sormuras]

Follow-up from #33 and https://travis-ci.community/t/cannot-install-oracle-jdk-11/3892/4?u=sormuras

Deliverables

• Remove BCL from license option
• Remove 9-BCL, 10-BCL, and 11-BCL URLs from script
• Forward to OpenJDK variant ?

[sormuras]

/cc @travis-ci @BanzaiMan

[tellison]

You can obtain your OpenJDK builds (nightlies or releases) via the AdoptOpenJDK API. No login page etc to go through.

If there is anything missing from there drop a note on the #api channel of AdoptOpenJDK Slack and the team can discuss options.

[sormuras]

Thanks for the heads-up, Tim.

I'm already using and showing examples how install-jdk.sh supports AdoptOpenJDK builds via its API here:

https://github.com/sormuras/sormuras.github.io/blob/686e757e20aff3a32f69b324326213cf3b123758/.travis.yml#L28-L33

source install-jdk.sh --url 'https://api.adoptopenjdk.net/v2/binary/releases/openjdk11?openjdk_impl=hotspot&os=linux&arch=x64&release=latest&heap_size=normal&type=jdk'

I wished, https://jdk.java.net/ had a similar API (/cc @robilad) or at least a look-up table -- so I didn't have to parse their HTML document for the download links...

Having said that, I don't plan to change install-jdk.sh's API to directly support AdoptOpenJDK, yet. But it would be an easy task for @travis-ci (/cc @BanzaiMan) to update their scripts accordingly, i.e. map user's configuration settings to a command line as shown above.