merge into refactorized classes: empty mosaic work

ImageMosaicWalker refactorization

add useExistingSchema parameter

minor fix

fix imagepiramyd

fix updateCatalog

fix merge with: empty mosaic

fix usage for ImageMosaicDatastoreWalker. Create a test for UseExistingSchema.

remove unused test

close datastore iterator

fix tests on windows switching to shp file

minor review with some small refactor

improve tests

merge with master

fix netcdf tests on auxiliary files
Merge pull request #309 from ccancellieri/master-GEOT-4597-create-mosaic-existing-schema

merge into refactorized classes: empty mosaic work