First pass at adding array support to ESJsonEncoder.
All field types now support arrays in ESJsonEncoder.
Removed reflection from writeRawArrayField.
Replaced writeRawArrayField with generic writeField.
Added tests for raw fields
Writing raw String and Bytes fields will now work with arrays.
Renamed writeRawField to writeIntField.
envversion is now written with writeStringField.
Updated changes file to reflect that ESLogstashV0Encoder was updated as well.
Merge pull request #932 from ianneub/ESJsonEncoder_array

Added string array support to ESJsonEncoder