Issue with documentation for air-gapped installation of CPD 3.5.x

[hnielens]

Looks like there is a problem with the documentation for the air-gapped installation of CPD (linking doc pages). So main page is the

• README.md. It points in step 6 to the installation of CPD section: https://github.com/IBM-ICP4D/cloud-pak-ocp-4/blob/master/doc/install-cp4d-35.md
• The installation of CPD page then first talks about connecting to the cluster etc.. until it reaches the actual steps for installing CPD in a connected scenario: https://github.com/IBM-ICP4D/cloud-pak-ocp-4/blob/master/doc/install-cp4d-35.md#install-cloud-pak-for-data-connected
• In the first line of that heading actually says to skip and go further down in the same page to the airgapped installation steps: https://github.com/IBM-ICP4D/cloud-pak-ocp-4/blob/master/doc/install-cp4d-35.md#air-gapped-install-of-cloud-pak-for-data
• There we immediately start unpacking a tar file which we never seem to have created and it is assumed that cpd-cli is already installed further down, which we skipped earlier.

Now there is a seperate page in the docs folder that discusses the air-gapped installation, including how to install the cpd-cli, download (preload-images), tar them and but it seems not be linked anywhere from the structure starting in README.md: https://github.com/IBM-ICP4D/cloud-pak-ocp-4/blob/master/doc/install-cp4d-35-airgapped.md. That page discusses everything well up to shipping the tar file to the air-gapped bastion node.