allow multiple image upload from gallery

[sandrozbinden]

• evaluate android https://github.com/wymsee/cordova-imagePicker)
  (Plugin is working scrollbar is annying but everything works really good multi upload was working with just a few code changes)
  exif data is missing
• evaluate ios https://github.com/wymsee/cordova-imagePicker)
  (Plugin is working with ionic view app everything looks quite good the ios way is definitly nicer)

With plugin photo library we would have to create our own library no native

• evaluate android https://github.com/terikon/cordova-plugin-photo-library)

• evaluate ios https://github.com/terikon/cordova-plugin-photo-library)

• replace plugin -> maybe write a new plugin that takes original

• allow multiple selection

[sandrozbinden]

to try it out just use the multi upload branch

[mleu]

must be reestimated due to technical limitation of current plugins
(was 3 points in sprint 12)