Fix optional-components installation for 2.3+ images.

[vinayakumarb]

Following changes are done in this;

1. Running ./install_optional_components.sh in its own session to avoid any conflicts in loaded variables.
2. Correcting the mapping of user-visible optional-component name to component names used inside image.
3. Setting DATAPROC_IMAGE_TYPE and DATAPROC_IMAGE_VERSION used inside some of the scripts.

[cjac]

I was stuck on my review of the base image generator today. I'll try to get to this one this week.

[vinayakumarb]

I'm still working on running this where I can access the 2.3 images, but there's one item I'd like addressed. The regular expression does not support major.minor.subminor-OS format

As mentioned, major.minor.subminor-OS is available for base image to be selected.

[vinayakumarb]

Thanks @cjac .