Show altruistic key in custom install builder

[choksi81]

The current custom install builder lets users generate new sets of keys or upload existing ones for inclusion in the installer. A small percentage of each custom install remains reserved for Seattle infrastructure purposes (usually called "service vessel" I think), but no resources are provided for random clearinghouse users.

I propose to show per default the "altruistic" public key, and ask the person building the custom installer to allot some percentage for that key. This lets our clearinghouse access that vessel, and set it up for general public use. The key should be properly labelled (footnote/anchor maybe), explaining how altruistic donations help grow the system.

[aaaaalbert]

One thing we need to make sure is whether the clearinghouse requires an altruistic node to be set up (i.e. vessels split) by the clearinghouse itself. I think that for a plain altruistic install, the CH creates a database entry for the node; not sure if this entry is later required when handing out / assigning resources to CH users.