Hide keyboard on next button click

[shankarpriyank]

I thought it might a minor improvement in the UX if the keyboard is hidden on next button click, as there are a lot of cases in which a dialog box might appear and dialogboxes and keyboard do not look together, but again its just my personal opinion.
Just added a couple of lines to hide the keyboard on next button click

[shankarpriyank]

Also @nicolas-raoul, uploading of images is not working at all for me.
I tried it with all sort of images, they all just fail. not sure why are they failing though

[nicolas-raoul]

Actually we want to encourage people to write captions specific to each picture.
For instance if they upload 3 pictures, it would be better if they enter a different caption for each.
Hiding the keyboard on "Next" would add one step for entering a specific description, and thus would go against that goal... if anything, forcing the keyboard to be visible on Next might be better, feel free to create an enhancement issue about that. Meanwhile I will close this pull request, but part of the code can probably be reused in the future so please mention its URL if you create the issue.

About uploading: Current master should work much better now. :-)

Thanks! :-)