Standardized colors, margins and text size

According to http://developer.android.com/design/style/metrics-grids.html, http://developer.android.com/design/style/typography.html and http://developer.android.com/design/style/color.html. 

Nearly all changes are replacing, or rounding, text size, margins and paddings to fit the standards ones. 
The only other change are the removal of IDs to the image views in `activity_about`, because they were all the same, which gave me an error. I removed them instead of replacing them because there is no need to attach an ID to the images.