- Implemented copying of custom expressions to other simulations in expression builde...

- Implemented copying of custom expressions to other simulations in expression builder dialog. Note the small changes to various files are to allow simulations access to parent document.
- Switched to unicode char escapes
- Removed dynamic setting of flightdatatype priority
- Now hiding up down arrows in custom expression pane when unusable
- Localized custom expression operator discriptions.

git-svn-id: https://openrocket.svn.sourceforge.net/svnroot/openrocket/trunk@770 180e2498-e6e9-4542-8430-84ac67f01cd8