set RenderStyle itself as current
rendertheme: merge AttributeMatcher into Rule

- allow to match actual key-value-pairs.
  previously value matcher just checked *any* value not
  the one that matched key. See PositiveRuleKV/MultiKV
merge Positive/NegativeRule into Rule
move RuleBuilder xml part to XmlThemeBuilder
add StyleBuilder interface
add RuleBuilder setters for Rule- and Style-Builders
move ThemeBuilder
no more Rule stack optimization

- the modified xml schema allows write proper rules :)
update file header
Merge branch 'rule_refactor'