Ensure loading... message closes upon completion or error

git-svn-id: http://svg-edit.googlecode.com/svn/trunk@2865 eee81c28-f429-11dd-99c0-75d572ba1ddd
Rename labels to fix issue 1206 of confusing labels ("Open Image"->"Open SVG" and "Import SVG"->"Import Image")

git-svn-id: http://svg-edit.googlecode.com/svn/trunk@2867 eee81c28-f429-11dd-99c0-75d572ba1ddd
Add a custom.css stylesheet for customizations not requiring modification of the main editor

git-svn-id: http://svg-edit.googlecode.com/svn/trunk@2869 eee81c28-f429-11dd-99c0-75d572ba1ddd
Add reference to custom.css in appcache

git-svn-id: http://svg-edit.googlecode.com/svn/trunk@2871 eee81c28-f429-11dd-99c0-75d572ba1ddd