Added detail to themes to cover all h*'s, etc.

A number of HTML elements were using Poole defaults where Hyde Base16 themes seemed more sensible. I've added quite a few elements to each theme to make all elements consistent with the applied theme.

There is also a new theme, a nicer (IMHO) blue.

I've also added a default post-title color, but I do not remember why I did that. Use or lose, either way is fine.