added better comments/doctests for parse_[template/arg] funcs
added better comments/doctests for parse_[template/arg] funcs

mbmcgarry/cyclus,hodger/cyclus,Baaaaam/cyclus,rwcarlsen/cyclus,Baaaaam/cyclus,rwcarlsen/cyclus,mbmcgarry/cyclus,hodger/cyclus,gidden/cyclus,gidden/cyclus,mbmcgarry/cyclus,rwcarlsen/cyclus,mbmcgarry/cyclus,hodger/cyclus,hodger/cyclus,rwcarlsen/cyclus,gidden/cyclus,hodger/cyclus,Baaaaam/cyclus,gidden/cyclus