refactor(css): move most of the CSS to BaseBundle

looking through the existing CSS code and sorting selectors into the
BaseBundle. Files inside specific Bundles now only should contain
selectors only to be used inside that Bundle. Everything else is moved
or has a corresponding -base.less file inside BaseBundle.
Example:
everything basic about forms is found at: BaseBundle -> custom-form-base.less,
all variables, such as colors, border-width, ..., are at CharityBundle
-> custom-form.less