fix tab order for password settings

tab order defaults to the order widgets are created - and not the order
they're added to the grid widget.

Reordered code to bring creation + adding of Widgets in sync.
use ShareDialog for VeloHero and Trainingstagebuch

adjusted velohero + Trainingstagebuch upload to use new ShareDialog
ShareDialog optimizations

introduced a base clase for the individual uploaders to reduce code
duplication.

This made it possible to
- default to download a ride to a service if it wasn't uploaded, yet.
- grey out checkboxes for services without credentials
Merge pull request #1132 from rclasen/sharedialog

use Sharedialog for Trainingstagebuch + VeloHero, further improvements