Fixed history and header update in IE

Due to Internet Explorer caching GET requests the Undo/Redo list and
column headers were not updated, leaving essential parts of the user
interface crippled even if Google Frame is installed. Adding
Cache-Control headers to the responses fixes this.
Merge pull request #665 from Arcadelia/IE_Cache-fixes

Fixed history and header update in IE by setting "Cache-Control", "no-cache" in HTTP headers