add gitignore for java
add gitignore for java

ethereumj/ethereumj,chengtalent/ethereumj,ddworken/ethereumj,BlockchainSociety/ethereumj-android,shahankhatch/ethereumj,swaldman/ethereumj,fjl/ethereumj,swaldman/ethereumj,syng-io/ethereumj-android,loxal/FreeEthereum,caxqueiroz/ethereumj,gerbrand/ethereumj,loxal/FreeEthereum,vaporry/ethereumj,loxal/FreeEthereum,ethereumj/ethereumj,loxal/ethereumj