Add ability to enumerate variables in bash

[espenwa]

This PR adds the ability to enumerate variable names (and subsequently get their value) in bash:

for variablename in "${OCTOPUS_VARIABLENAMES[@]}"
do
  echo ${variablename} = $( get_octopusvariable "${variablename}")
done

Due to limitations in bash, returning an array from a function is not practical, and hash-objects/dictionaries does not exists. The implementation is therefore done by adding a global array with variable names. Not very elegant, but is apparently working. Two tests added.

Current implementation does not use encoded (base64) variable names, as get_octopusvariable expects un-encoded variable name. This might result in obscure characters in the variable name (mainly ") breaking the script. Making OCTOPUS_VARIABLENAMES contain encoded variables is trivial, but will require an additional function call to get the un-encoded variable name before calling get_octopusvariable (or some other means to counter the fact that get_octopusvariable encodes the name before doing the lookup).

[CLAassistant]

All committers have signed the CLA.