Add "normal", optparse-style options to swift-ring-builder add.

The old format is still present and works just like it did before, so
your existing scripts won't break.

New format pros:
 * it's readable even for Swift newcomers
 * it's easy to extend
 * it's familiar to anyone who's used a Unix command line
 * we don't have to maintain the parser

New format cons:
 * you can't add multiple devices in one go

Old format pros:
 * you can add many devices with one command
 * it's compact

Old format cons:
 * it confuses newcomers
 * "wait, is that zone dash IP colon port slash device, or zone slash
   IP dash port colon meta underscore device?" Just try walking
   someone through adding a device over voice chat.
 * it's annoying to add new fields

Note that this only affects the command "swift-ring-builder
<builderfile> add". Other swift-ring-builder commands are unchanged.

DocImpact

Change-Id: I034b7f79eb6f4d81a5c4da193e1358741441c5b5
Merge "Add "normal", optparse-style options to swift-ring-builder add."