[PATCH] Add support for JPL tiledWMS protocol

[lplesea]

Raster support for TiledWMS, as described at  http://onearth.jpl.nasa.gov/tiled.html Driver is implemented as a minidriver for the WMS GDAL driver. The initialization sequence of the WMS GDAL driver needs to be modified to allow for server defined tiles. The minidriver supports byte and short datatypes, server described projections and variable parameter tile sets.

[lplesea]

A few bug fixes

[warmerdam]

I'm going to take a crack at this.

[warmerdam]

Patch applied (r21702). Added some docs, did a bit of reformatting, and skipped some of the changes to handling of defaults for standard wms parameters.

Added brief testing (r21704).

[rouault]

r21705 /trunk/gdal/frmts/wms/ (minidriver_tiled_wms.cpp minidriver_tiled_wms.h): Fix errors in tiled WMS driver (#3493)

[rouault]

r21707 /trunk/gdal/frmts/wms/wmsdriver.cpp: WMS: be robust to failed dataset initialization (#3493)

[rouault]

r21725 /trunk/gdal/frmts/wms/minidriver_tiled_wms.cpp: TiledWMS: fix memleak on frmt_twms_daily.xml sample

r21726 /trunk/gdal/frmts/wms/ (minidriver_tiled_wms.cpp minidriver_tiled_wms.h): TiledWMS: avoid segfaults when parsing corrupted/hostile server response (#3493)

[rouault]

r21727 /trunk/gdal/frmts/wms/minidriver_tiled_wms.cpp: TiledWMS: (style change only) use NULL for null pointers instead of 0

r21728 /trunk/gdal/frmts/wms/minidriver_tiled_wms.cpp: TiledWMS: replace unsafe test for empty C++ strings based on testing [0] by proper call to empty() method (#3493)

[rouault]

r21851 /trunk/gdal/frmts/wms/minidriver_tiled_wms.cpp: TiledWMS: fix crash on serverUrl =  http://wms.jpl.nasa.gov/wms.cgi and TiledGroupName?=Continental US Elevation due to too strict epsilon value (#3493)

[rouault]

r21852 /trunk/gdal/frmts/wms/minidriver_tiled_wms.cpp: TiledWMS: fix logic error introduced in r21728 (#3493)

[rouault]

r21877 /trunk/gdal/frmts/wms/dataset.cpp: WMS: restore local disk cache capability, that was gone with r21702 (#3493)