ACME-1277 : Final set of filters, added a SnapshotFiltersEnabled debug setting

indra/integration_tests/llimage_libtest/filters/heatwave.xml

.../integration_tests/llimage_libtest/filters/julesverne.xml

...a/integration_tests/llimage_libtest/filters/lensflare.xml

indra/integration_tests/llimage_libtest/filters/overcast.xml

indra/llimage/llimagefilter.cpp

indra/newview/app_settings/filters/Autocontrast.xml

indra/newview/app_settings/filters/LensFlare.xml

indra/newview/app_settings/filters/Miniature.xml

indra/newview/app_settings/filters/Spotlight.xml

indra/newview/app_settings/filters/Toycamera.xml

indra/newview/app_settings/settings.xml

indra/newview/llfloatersnapshot.cpp

indra/newview/skins/default/xui/en/floater_snapshot.xml

indra/newview/skins/default/xui/en/strings.xml