Restructure the css to enable easy themes implementation

[vegegoku]

This change along with the restructure of the css will bring a new minimalist theme to the library and will make material design an optional theme, the demo will still go with the material design theme and will be the default theme, but using other themes or the minimalist theme will be possible.

this will also ensure the separation between styling and functionality of elements. and will ensure that the library is not bound to material design specification and can be extended to meet different needs.