Moving to consistent use of '-' (dashes) in XML properties

[artemp]

We currently have mixed use of dashes and underscores in XML property names, which makes it difficult for stylesheet authors to remember property names (or easy to misspell).

Because Mapnik2 has other breaking changes, now is the time to do this.

I propose we move fully to using '-'/dashes when property names should have a break (to fit css style). Properties in python (and other potential binding languages) will consistently continue to use underscores.

Properties already using '-':
{{{

map level

background-color
background-image

metawriters

default-output
output-empty
meta-writer
meta-output

shield symbolizer

text-opacity

line symbolizer (stroke)

stroke-width
stroke-opacity
stroke-linejoin
stroke-linecap
stroke-dashoffet
stroke-dasharray

polygon symbolizer

fill-opacity
}}}

[artemp]

[springmeyer] I want to deal with this for the Mapnik 2 release, so we get consistent and avoid this issue in the future.

[artemp]

[springmeyer] good info here: http://stackoverflow.com/questions/1478486/using-in-xml-attribute-name

[artemp]

[springmeyer] added snapshot of trunk in r2575 that is pre-this change.

forward compatibility with this change has landed in mapnik 0.7.2: r2579

[artemp]

[springmeyer] landed in r2582, upgrade_map_xml.py updated in r2583, and basic change noted at https://trac.mapnik.org/wiki/Mapnik2/Changes