DICE Bash environment

RAT and MPU Unit share responsibility for the bash environment on DICE. We customise it from stock SL7 in a few ways:

• bashdefenv [link tbc] - involves patching bash to read a few additional environment files on startup
• CrichtonForComputingStaff - Crichton, which handles repsonses when commands aren't found
• BashTabCompletion - we augment the standard tab completion with help for DICE-specific tools and hosts
• CoUtils - Additional DICE-maintained utilities

-- GrahamDutton - 23 Oct 2019