refactor: move icon-render into directives/bits
chore: implement scaffolding for a main menu
feat(combat): persist combat counter across all maps
chore: add debugging and error checking to feature ids

- Treasure/Encounter features have persisted data, so they require IDs.  Log an error if a map is loaded with features that don't meet this requirement.
chore: fix treasure errors in sewer map
maps: move bryarlake chest out of reach

- fill it with 5000 gold, for anyone clever enough to get it.
feat: support caching google spreadsheet data

- putting /?dev on the game URL will force it to load data from Google during page load.  This is good for when tweaking game data in the spreadsheet and hot-reloading to test changes.
style: slightly better looking and more functional main menu
feat(sprites): support writing sheet source info as json
style(storeView): old working copy tweaks

- looks better than when stashed.   :shipit: