Refactor plot.js

[supunkamburugamuve]

The current plot.js need to be refactored and its functionality should be separated to clear functions where we initialize things, process things and modify things

[pulasthi]

Code of plot.js is refactored in the master. All functions are clearly separated into groups according to what the function does. Further refactoring can be done in to remove several flows that are repeated for timeseries and single graphs.