Support for intuitive responsive state syntax

[tenphi]

Currently to make responsive values inside state you should write something like:

<nu-block fill="bg :hover[special]|bg :hover[hover]"></nu-block>

It's more intuitive to write it like:

<nu-block fill="bg :hover[special|hover]"></nu-block>

It introduces a lot complications but I am sure they can be overpassed.

[tenphi]

Complex syntax is also supported now.

<nu-block fill="bg|subtle :hover[special|hover]"></nu-block>

or even (same result as above):

<nu-block fill="bg :hover[special|hover]|subtle"></nu-block>

normalization will look like:

<nu-block fill="bg :hover[special]|subtle :hover[hover]"></nu-block>