+ cleanup include directives
+ fixes and improved error handling
+ fix crop width/height calc
webp_reader : implement reading from file
type_from_filename : add webp support
+ update image_io test to support WEBP
+ image_reader : consistent error handling - throw image_reader_exception rather than returning 0 pointer.
disable the hsla image-filter - not yet ready for primetime
Add a couple more float to string conversion tests

See #1811
Merge branch 'master' into image-readers-c++11
+ add getBytes() method ( needed by webp i/o)
+ add webp writing support
+ add webp support
+ output webp

quality=100 -> demo.webp
quality=80  -> demo-med.webp
qiality=50  -> demo-low.webp

TODO: support other webp writing options
Merge pull request #1814 from strk/master-more-float-tests

Add a couple more float to string conversion tests
fixup postgis null comparision tests
add missing exception translator for datasource exceptions by catching std::exception - closes #1816
add test for #1816
fix spelling of unknown
also translate std::out_of_bounds => IndexError otherwise new std::exception => runtime catch will override - refs #1816