Improve code reuse in Single and Double Template definitions

[nicobees]

Possible code to reuse:

• data table creation for the lens spec section
• entire method for the lens spec section

Possible things to improve:

• naming of some methods
• positioning of private helpers methods
• handle margin between sections at page_build level, so that each single section can possibly receive left and top margin (optional params, only if they are set then the method will set them)