PERF: Remove calls to Update() and replace with calls to UpdateOutputInformation(), which will compute the stats without processing the full image result in memory

PERF: Move statistics estimation code out of GenerateData() to allow for a call to UpdateOutputInformatio() that will compute the stats but not the result on the full image.

ENH: OTB-applications wrappers: initialized directory of file-dialog openend when using browse button with edited text.

ENH: Moved otb::Wrapper::QtWidgetOutputFilenameParameter::SetFileName() and ::QtWidgetOutputVectorDataParameter::SetFileName() into public slots section.

COMP: Adding a new method in the version proxy to wrap the GetDriver()->GetName() code, and use it in Segmentation application

Two different methods for computing margin and confidence in random
forests.
Refactor the vote count in a separate method.

- Move declaration of GDAL_CONFIG_CHECKING in otb-module-init.cmake to ensure gdal configuration in all cases (if statement)
- OTBCommon module needs to depend on OTBGDAL as GDAL module has to set OTB_USE_GDAL_20 before configuring otbConfigure.h
- Set mode to STATUS for GDAL version >= to 2.0

All these issues were found compiling gdal trunk (2.1.0dev) with clang 3.5.

PERF: Try to remove replacement of * (1/bandwith) with / bandwith to see if it improves tests stability