Release 0.1.5

New:

 * [account] allow upgrade of an account from instance
 * [operation] upgrade an account
 * [price] allow orders to be deleted
 * [config] allow to iterate all elements in the database
 * [docs] add more documentation as requested #2
 * [bitshares] allow to approve a list of proposals
 * [txbuilder] construct tx prior to adding additional data
 * [bitshares] new call for price feed production
 * [price] allow for jsonification of price and asset objects
 * [feed] proper feed<->witness relations
 * [price] allow dividion of Price instances - for ratios
 * [vesting] allow claiming of vesting shares directly

Fixes:

 * [fix] memo needs an extra str()
 * [newfeed] allow to neglect cer rate
 * [cancel] allow cancelation of multiple orders in order transaction
 * [feed] also invert the CER if needed
 * [price,notify] Fixes for deleted orders
 * [notify] properly deal with deleted orders
 * [memo] fix invalid memo structure #3
 * [price] remove irrelevant space
 * [price] don't know the order id of handed over only Amounts
 * [price] properly load Assets for price
 * [proposal] raise error if proposal does not exist
 * [proposal] default proposal expiration set to 1 day
 * [proposals] Allow to explicitely define the proposal expiration with prosoal_expiration variable
 * [price] fix missing variable for args[0]
 * [price] fix ticker priceChange
 * [bitshares] price feed ensure order of price feed and proper assets
 * [txbuilder] fix a copy/paste error
 * [price] use proper fractionalization
 * [account] history deal with the history differently
 * [Witness] more detailed data