Various fixes which should probably be broken into multiple commits:)

Various fixes which should probably be broken into multiple commits:)
- Changed the way the ProgressDialog is dismissed from using some non-functional reflection code, to using a FragmentTransaction (which works)
- Added code which shows the save button only when the CurrentRocket is modified.
- Broke the save functionality into a Fragment with background Task so it is more reliable.

git-svn-id: https://openrocket.svn.sourceforge.net/svnroot/openrocket/trunk@808 180e2498-e6e9-4542-8430-84ac67f01cd8