Home page and Accomplishment page's area plot refactoring

[onlyphantom]

The data wrangling code to produce area plot leaves a lot of intermediate object floating around and are quite (unnecessarily) verbose.

My estimate is that the data wrangling code could be at least 40% lesser: lesser code -> higher maintainability

Specific objects to optimise:

• g.accum for accum_global() function.
• g.accum_personal for accum_personal() function.