For settings the CORS response headers you can create a filter in Magnolia that
adds the needed settings to the response object.
--
Context is everything:
http://forum.magnolia-cms.com/forum/thread.html?threadId=4ad95728-9c0c-4b27-b544-58be8a042158
There's documentation using JetBrains IDEA and Git on the community wiki, maybe
it can help you even when using Eclipse:
http://wiki.magnolia-cms.com/display/WIKI/Development+environment+using+IDEA
--
Context is everything:
http://forum.magnolia-cms.com/forum/thread.html?threadId=f14856c9-964