Create a docker support page to provide solutions to encountered problems

[bjagg]

Is your feature request related to a problem? Please describe.
In a new training exercise, several Docker issues surfaced but we came up with solutions. We need to capture these for the community.

Describe the solution you'd like
New document page to cover Docker.

[bjagg]

Docker can be installed for privileged users (i.e. root). It should be installed for the user account that will be performing builds.

[bjagg]

On CentOS, Docker required a configuration change to work with uPortal-start. The socket approach needed to be changed to using ports instead.

[bjagg]

Swam configuration was causing an issue. Removing it from the user's default config file helped.

[bjagg]

When creating Demo/CLI images, HSQL must be stopped. The lock files in .gradle/hsqldb/ are copied to the dockerimage which prevents HSQL from starting when the docker image is spun up.

[bjagg]

Custom skins break the Demo docker image.

[bjagg]

Build breaks when using older Docker versions (which ones?)

[bjagg]

Where are the generated Docker images?