When logging in and receiving a reply that isn't understood, show a more informative error message.

`tr() + tr()` for better translation flexibility.

As seen in this image, you cant see where you are logged in.

How it looks now:

Syntax correction.

As per @daenyth’s comment:
https://github.com/Cockatrice/Cockatrice/pull/792#issuecomment-76593730

This is the first implementation of a theme manager. It’s a rebased and
revisited version of #792.

 * Refactored code out of common/ into servatrice/
 * added smtp client library
 * disable registration when connected
 * validate email address
 * send activation token via email

fixed welcome msg
added some articles
added database phrase to card updater
cosmetic changes to the description in edit sets

 * added missing bits of serverside code;
 * added fronted in client;
 * removed demo python scripts;

It failed if the path contained spaces.

As per @daenyth’s comment:
https://github.com/Cockatrice/Cockatrice/pull/792#issuecomment-76593730

This is the first implementation of a theme manager. It’s a rebased and
revisited version of #792.