Come clean about agent args in site-config

[mhasself]

Most examples of agent arguments for site-config have the key, value pairs carefully grouped, e.g.:

[['--arg1', 'go'], ['--arg2', 'blerg']]

but for a long time now it's been possible to simply pass in a flat list:

['--arg1', 'go', '--arg2', 'blerg']

At this point we should probably just also accept strings, though the code does not currently do so;

'--arg1 go --arg2 blerg'