rounded corners for chapter box (and a little extra)

To make this work in Firefox the chapter table can not have its borders
collapsed and rows can not have background set.

* All backround rules for rows applied to cells instead.
* Replaced ```border-collapse``` with ```border-spacing:0;```.
* Minor CSS enhancements and cleanup

.gitignore

* ignore IDEA IDE settings folder
* Removed unnecessary asterisk in front of ```.DS_Store``` and
```Thumbs.db```