implemented generation of qrcode for receiving payments by scanning it

+ shared view with shared helper
+ custom model with validation and methods for creating it
improved buttons
added validation and btc address validator
fixed enabled button without any wallets
fixed saving of wrong address
validations added
layout: added hr
more D.R.Y: introducing partials for various errors or hints
added centered class
renamed
imroved layout
improved layout and added "time ago"