Add bootstrap

Signed-off-by: Diego Pasqualin <dpasqualin@c3sl.ufpr.br>
dpll.html: Improve layout

Signed-off-by: Diego Pasqualin <dpasqualin@c3sl.ufpr.br>
dpll.html: Check Step-By-Step checkbox as default

Signed-off-by: Diego Pasqualin <dpasqualin@c3sl.ufpr.br>
Rename dpll.html to index.html

Signed-off-by: Diego Pasqualin <dpasqualin@c3sl.ufpr.br>