README: Fix link to installation instructions
Optimisations: @depend_property
Optimisations: global @depend_property

-  if main key has never values we can ignore its dependend properties
   completely
Optimisation: @style_element_property: generate db rows only when prop is set
pgmapcss_compile_where: use @style_element_property for list of props
Eval: new functions zoom() and scale_denominator()
Eval: Bugfix boolean()
Eval: new function area()
pgmapcss_compile: Bugfix, set current pseudo_element_ind on final checks
Eval: new function switch()
Eval: new function power()
Eval::boolean: bugfix (detect 0 as false)
Eval: new operators (functions): && (and), || (or), ! (not); fix priorities
Conditions: accept '.' as valid character for tags
Default Base-Style: add parameters 'offset' and 'casing-offset'
Create 'Default Base-Style' for Mapnik branch stroke-width-expr