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
Improved resource resolver thread handling to prevent thread leaks
Merge pull request #309 from ccancellieri/master-GEOT-4597-create-mosaic-existing-schema

merge into refactorized classes: empty mosaic work
Improve contributor guidelines
Manual merge of pr/286 from Mike Benowit
Merge branch 'contributing' of https://github.com/aaime/geotools into aaime-contributing
replace hack page and separate out role from procedure
Clarify small / large contributions and test cases, remove invitation to contact module maintainers directly.
Merge pull request #311 from jodygarnett/contributing

Improve Contributor guidelines
Another GEOT-3407 related fix
[GEOT-4609] Unclosed iterator in VectorToRasterProcess
[GEOT-4606] different offsets for same dash-stroke
sort out contributor role with clear advantages, responsibilities and procedure
Fix CSV tutorial to use "the_geom" and explain shape file limitations
Feedback from andrea and fix up the tutorial text to match
Merge pull request #313 from jodygarnett/geot_4595

Fix CSV tutorial to use "the_geom" and explain shape file limitations (GEOT-3595)
feedback from andrea on advantages of being a module maintainer
Merge pull request #312 from jodygarnett/contributor

sort out contributor role with clear advantages, responsibilities
GEOT-2333: removeSchema
Merge pull request #308 from geosolutions-it/GEOT-2333

GEOT-2333: removeSchema