CXX-175 ensure bulk operation executed if write fails
CXX-180 Generate _id automatically for InsertWriteOperations
minor: make InsertWriteOperation constructor explicit
Addition of GridFileBuilder class for on-the-fly writting of data to GridFS.

- Added GridFileBuilder
- Added unity test for GridFileBuilder
- Updated code style
- Updated with coding style changes and addition of _insertChunk private method in GridFS
CXX-186 Add group command helper
CXX-186 Use StringData, improve comments, take refs
minor: adjust version test for dyslexic versionCmp