Add developer options tab, add option to save internal guider images.

Two things:

• add a new KStars Options tab called developer, for things users probably don't want to do
• add a logging option to that developer tab to save internal guider images. This, of course, would not be used regularly but only when debugging guider issues.
• moved the option to save focus images from the logging menu and into the developer options tab.

As part of this, I needed an icon for the developer tab. I drew the image of the hammer.