Dutch localization (nl_NL) update
Localized "invalid_password" to PL
Fixes a broken pdf link for kdchart.pdf
Merge pull request #3259 from colbat/broken-pdf-link-kdchart-fix

Fixes a broken pdf link for kdchart.pdf
Merge pull request #3245 from piotrex/patch-3

Localized "invalid_password" to PL
Merge pull request #3241 from timvandermeij/dutch-localization-update-may-10

Dutch localization (nl_NL) update