Merge pull request #548 from sutra/develop

Upgrade maven license plugin to 2.6 and attach license check to validate phase
added an ignore plugin execution for Eclipse for the new  license-maven-plugin addition.
format code
Add constant BTCChinaExchange.DEFAULT_MARKET.
Implement BTCChina buyIcebergOrder and sellIcebergOrder API methods.
Implement BTCChina cancelIcebergOrder API method.
Implement BTCChina getIcebergOrder and getIcebergOrders API methods.
Change order ID type from long to int, to make consistent.