Add Logging Support
This change adds support for log levels. There are three levels of
logged messages: always, verbose, and very verbose.
Change Price Source
Change the source of price information to eve-marketdata.com from
eve-central.com. eve-marketdata provides volume information which
will be helpful in the future.
Add Volumes for Inventable Items
The result list now displays the volume of items moved through Jita.
EveIndustry.fetchPriceData was refactored a bit to allow it to generate
deferral requests on different APIs.