css language enhancements

[FabioDiMonte]

Lots of CSS syntax recognition enhancements, including:

• grouping feature (explained in examples below)
  • eg:
    2em -> constant.numeric
    2em -> keyword.unit.relative
  • eg:
    a, .myClass, span.extra {...} -> selector
    a, .myClass, span.extra {...} -> entity.name.class
• attribute selector
  • eg:
    input[type=button] -> selector
    input[type=button] -> entity.name.tag
    input**[type=button]** -> entity.name.attribute
    input[type=button] -> support.attribute-name
    input[type=button] -> support.text-value (or string if inside quotes)
• media queries (full grouped syntax, including mediaquery.feature , mediaquery.expression, ...)
  • eg:
    @media not print and (max-width: 1160px) {...} -> media-query
    (at)media not print and (max-width: 1160px) {...} -> at-directive
    (at)media not print and (max-width: 1160px) {...} -> mediaquery.query
    (at)media not print and (max-width: 1160px) {...} -> mediaquery.reserved
    (at)media not print and (max-width: 1160px) {...} -> mediaquery.type
    (at)media not print and (max-width: 1160px) {...} -> mediaquery.expression
    (at)media not print and (max-width: 1160px) {...} -> mediaquery.feture
    (at)media not print and (max-width: 1160px) {...} -> constant.numeric
    (at)media not print and (max-width: 1160px) {...} -> keyword.unit.absolute
• css methods (like rgb(), url(), linear-gradient() )
  • eg:
    background-image: url(/path/to/image.jpg); -> css-property
    background-image: url(/path/to/image.jpg); -> css-method
    background-image: url(/path/to/image.jpg); -> method-name
    background-image: url**(/path/to/image.jpg); -> method-params
    background-image: url(/path/to/image.jpg**); -> constant.path (or string if inside quotes)
• exceptions (ie: !important)
• IE hacks recognition

.. and much more!

[FabioDiMonte]

some screenshots made using the code in this PR (including the changed CSS theme "solarized dark")

most of the css syntax now recognizable with rainbow

attribute selectors, pseudo elements and pseudo classes, media queries, css-methods...

IE hacks