i18n : add spanish, italian, japanese, korean and portuguese translations

Adding new translation in spanish, italian, japanese, korean and
portuguese, for all strings from mediaelement-and-player.js
i18n : update german, simplified and traditionnal chinese translation

Update translations in german, simplified and traditionnal chinese , for
all strings from mediaelement-and-player.js
Merge pull request #1310 from jalios/master

i18n : add new translations and update existing one