Sell by param (MythicalGames#27)

* enable sell by date as parameter

Start dgood 1 (MythicalGames#25)

* ids start from 1 instead of 0

* update build files

check against issued supply instead of current supply (MythicalGames#24)

actually log the sale

update spec for 1.1; add logsale method for history

adds time based minting (MythicalGames#21)

* add time based minting

* replace dgood_id generation from available_primary_key() to a one-use id function

* update README and example for time based minting

Merge pull request MythicalGames#20 from MythicalGames/improvements

Improvements

only check issue amount max if nft

update README for v0.4