[BUGFIX] Resolves path variables for internal states

Previously we kept path variables in our status variables
(like in webroot or current working directory). This lead
to unexpected behavior when changing the referenced path.
Lets each processor define if it wants to change cwd

SCSS processor does not want to have the working directory
changed to the processed file automatically.
Refactors css reading for better scss support

Prepared to load assets (imports and other urls) from
current working directory or from the parent file.
[BUGFIX] Fixes scss example
Adds more scss examples/tests