some fixes for small visual bugs in bootstrap layout

- form input error text when formstyle='bootstrap' has fixed width.
In narrow screens (see image):
- topbar has space in left and right sides;
- login button in topbar is unaligned.

![immagine](https://f.cloud.github.com/assets/3496662/775167/aeb1aa20-e96b-11e2-8bb8-7131c4b5a0fe.jpg)