Convert IGB File Choosers to native via the JavaFX widgets

We should convert the file choosers in IGB to native file choosers via the JavaFX widgets.

Below is a list of places where the file chooser appears in IGB. All of the following places should be converted to the native file chooser:

1. Open File… (under File Menu)
2. Open Genome from File…(under File Menu)
3. Save Image…(under File Menu)
***4. Load/Save Session (under File Menu) – Currently not using Native File Chooser
***5. Configure Weblinks, Import/Export (under Tools Menu) – Currently not using Native File Chooser
***6. Import/Export Bookmarks…(under Bookmarks Menu) – Currently not using Native File Chooser
7. Add/Edit Data Source, Choose local folder (in Data Sources tab of IGB Preferences)
***8. Personal Synonyms (in Data Sources tab of IGB Preferences) – Currently not using Native File Chooser
***9. Add... [App Repository] (in App Repositories tab of IGB Preferences) – Currently not using Native File Chooser
10. Save PAXML File… (in ProtAnnot file menu)

It may be helpful to refer to the release documentation for file choosers to make sure the file choosers are meeting their expected guidelines:
https://wiki.transvar.org/display/ITD/FileChooser