Add chooser to export interface to make available formats obvious

[GoogleCodeExporter]

The export system currently uses the file extension to determine which
format to use.  This needs to be converted to a chooser/combobox to make
the choices more obvious, with associated greying out or hiding of
irrelevant options.

Original issue reported on code.google.com by shawnlaffan on 4 Nov 2009 at 7:03

[GoogleCodeExporter]

Implemented in pre-release 0.11, svn update 1299.

Original comment by shawnlaffan on 5 Nov 2009 at 10:38

• Changed state: Fixed
• Added labels: ****
• Removed labels: ****

[GoogleCodeExporter]

Original comment by shawnlaffan on 5 Nov 2009 at 9:21

• Added labels: release0.11
• Removed labels: ****

[GoogleCodeExporter]

Note:  this is for BaseStruct objects only at this stage.  See Issue #34

Original comment by shawnlaffan on 5 Nov 2009 at 9:57

• Added labels: ****
• Removed labels: ****

[GoogleCodeExporter]

Original comment by shawnlaffan on 19 Nov 2009 at 10:57

• Added labels: Milestone-Release0.11
• Removed labels: ****

[GoogleCodeExporter]

Original comment by shawnlaffan on 20 Nov 2009 at 8:17

• Changed state: Verified
• Added labels: ****
• Removed labels: ****