Dockerfile improvements

[maxim-belkin]

Dockerfile:

• set name, version, and maintainer labels
• set DEBIAN_FRONTEND to noninteractive
• use --no-install-recommends flag for apt-get install
• sort installed packages alphabetically
• add automake and python2.7 packages
• properly clean up apt's cache
• move &&s to the beginning of lines for consistency
• Remove unnecessary mkdir -p /images/test/

configure.ac:

• Limit allowed Python versions to 2.7, 2.6, and 2.

[coveralls]

Coverage remained the same at 78.562% when pulling 5650236 on maxim-belkin:Dockerfile-improvements into 0cb62af on NERSC:master.