add LZW compression to MongoObjectDatabase
added bulk putAll

Reduces import of wsa_rivers from 327 to 176 seconds
Added paralellization to mongo objectdb putAll

reduces import of wsa_rivers from 176 seconds to 73
Upgrade mongo-java-driver from 2.12.1 to 2.12.2
Merge remote-tracking branch 'groldan/mongo_improvements'
Merge branch 'master' of https://github.com/boundlessgeo/GeoGit