Export dialog

[KRLango]

This is to solve issue: #932

I have given a single export the same workflow as multiple exports and tidied up the UI for the multiple exports as well:

• Emboldened sections titles for clearer separation
• Allowed the folder path to wrap to a second line to stop the dialog looking unbalanced
• Reordered the different options so the order matched the order in the output filename
• Removed the redundant prefix checkbox

[cmeyer]

Thanks! Merged and added an additional commit to make directory text expand to width of dialog if resized:
a399b59

[jamesrussell216]

Fixes #932