Refactor instances of greenBtn and greenBtns

[Vheissu]

Throughout the application we are using the class names greenBtn and greenBtns however, we are moving away from this green. All instances have been replaced with the colour background-color: #696FE4; but the class names are no longer applicable and should be renamed. Also, there is a lot of duplicated CSS code for these green buttons throughout copied and pasted. This needs to be refactored to only be defined once in the CSS (somewhere global).