Integrate contributed read/write GDAL KEA driver

git-svn-id: https://svn.osgeo.org/gdal/trunk@28011 f0d54148-0727-0410-94bb-9a71ac55c965
.travis.yml: add libkea building

git-svn-id: https://svn.osgeo.org/gdal/trunk@28012 f0d54148-0727-0410-94bb-9a71ac55c965
configure: fix typo in kea-config script name

git-svn-id: https://svn.osgeo.org/gdal/trunk@28013 f0d54148-0727-0410-94bb-9a71ac55c965
Merge .travis.yml