Error notification with error description

I have added notification about error in an alert message, so you'll never miss the problems. And it also outputs error info into status bar, shortly after the 'save' function finishes.
[this is my first ever pull-request, i'm not sure if i'm doing it right]

Example screenshot:
![Screenshot_1](https://f.cloud.github.com/assets/2082436/121390/8390a7f8-6d90-11e2-837d-41a645ff40a1.png)