bash-completion: add helper for appdata-from-desktop

Signed-off-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>
bash-completion: add helper for convert

Signed-off-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>
bash-completion: don't allow more than needed options for commands

Signed-off-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>
trivial: add myself to AUTHORS

Signed-off-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>
Merge branch 'wip/bash-completion'