Provide easy way of adding/modifying configs

[chicopaec]

When you use sandbox today it's hard to change the default values, like if you want to change the algod node to be an archival node, you'd have to change images/algod/setup.py and rebuild everything from scratch. It would be nice if sandbox up could support adding extra configs that would overload the existing default ones, or something similar.

[winder]

@chicopaec Many of the parameters are configurable with the config.* files, but not all of them. Aside from archival, which would definitely be nice for private network nodes, did you notice anything else missing?

[fionnachan]

Just encountered the same issue ^
Not urgent but would be nice if this behaviour is mentioned in the README

I tried to set the node to archival with an extra line in config.betanet but it didn't work

The only solution was to change Archival: false in this line to Archival: true

sandbox/images/algod/setup.py

Line 106 in 65238a9

f.write('{ "Version": 12, "GossipFanout": 1, "EndpointAddress": "0.0.0.0:%s", "DNSBootstrapID": "%s", "IncomingConnectionsLimit": 0, "Archival":false, "isIndexerActive":false, "EnableDeveloperAPI":true}' % (algod_port, bootstrap_url))

Would be nice if the config could be set from config.*

Other than Archival, Indexer is also a config that setup.py would override. Changing export INDEXER_DISABLED="{bool}" would not make any difference in my case with betanet.
(Also tried with lower case for both, & empty string for INDEXER_DISABLED)