Embedded HTML cleanups to improve readability

* Move template context retrieval to the top of the code block,
* Use format() to avoid mixing string with variables,
* Use implicit line continuation instead of endlessly concatenating strings,
* Use print as a function.

Obviously the HTML output won't look the same because we are
converting several print calls into just one. Once we move to
using external templates this will be fixed.

This a previous step to strip out the HTML into proper external templates.
Cleanup: Remove unnecessary function
Cleanup: Move complexity to another function
Cleanup: Remove unused function
Cleanup: Simplify options retrieval
Cleanups: Fix indents, remove blank lines
Move images to img/ directory

Fixes #9
Move CSS files to css/ directory

Fixes #10
Remove extra spaces