* rough auction type refactor
* replace endTime type
* split keeper file up
* update store methods
* move store methods to keeper.go
* move nextAuctionID from params to genState
* simplify auction type to not use pointers
* add basic auction tests
* update endblocker test
* add payout to depositors feature
* add more tests
* move index updates to Get/Set for more safety
* remove slightly unecessary ID type
* remove unused message types
* feat: add spec, update redundant type names
* stop sending zero coins
* use only one coins field in MsgPlaceBid
* remove uncessary Auction interface methods
* give auction types more accurate names
* remove vuepress comments from spec
* minor spec updates
* update doc comments
* add params validation
* code cleanup, address review comments
* resolve minor TODOs
* sync spec with code
Co-authored-by: Kevin Davis <karzak@users.noreply.github.com>
