Consolidate Dockerfile apt commands

[wcedmisten]

Summary

1. update and install commands should be on the same line, per official docs

Always combine RUN apt-get update with apt-get install in the same RUN statement.

2. cleanup should be in the same layer as install to reduce docker layer size. See discussion here
3. apt-get clean is redundant on images derived from Ubuntu base image. Same reference as 1)

Official Debian and Ubuntu images automatically run apt-get clean, so explicit invocation is not required.

[mtlynch]

Thanks!