matching column types via symbols instead of names
direct embedding: mapping to more generic slick types
direct embedding: symbol-based and easier to read method mapping scala to slick
direct embedding refactoring
direct embedding: symbol based mapping of main methods
direct embedding: added meaningful tests for || and &&. Remove incomplete implementation of size.
direct embedding: renamed -> annotation to slickOp(erator)
Merge pull request #149 from slick/tmp/matchSymbols

change slick backend to use symbols for matching on Scala trees (direct embedding)