Bug: Export, Unexport errors and options not implemented in `pico.go`

[kbdharun]

While I was working on updating the strings, I noticed that there are strings to display errors when exporting or unexporting binaries and applications. But, it doesn't seem to be implemented in pico.go.

Reference (from Pico in en.yml)

error:
    exportingApp: "An error occurred while exporting the application: %s"
    exportingBin: "An error occurred while exporting the binary: %s"
    unexportingApp: "An error occurred while unexporting the application: %s"
    unexportingBin: "An error occurred while unexporting the binary: %s"

[matbme]

Closed by #71