Add option to lupdate for detection of small changes

A new translation entry is generated also for small changes, that will likely not require any changes to the translations itself. This includes:

• Change of capitalization at beginning of words
• Remove additional whitespace
• Correcting typos
• Maybe adding or removing punctuation at the end

It would be helpful, if linguist could detect that there is a similar string, that is now unused, and take the translation from there.

This would reduce the work for translators.