Rework Build Parser handling

 * Rework IBuildParser:
    * Remove name() method.
    * Remove enterDirectory and leaveDirectory signals.
    * Allow chaining of parsers.
 * Rename IBuildParser to IOutputParser.
 * Implement GnuMakeParser.
    * Remove entering/leaving directory related code from all other parsers
    * Move filename fixup heuristic based on entering/leaving directory
      massages from gnumake here from AbstractMakeStep.
 * Add outputParser method to ToolChain: This removes the need to map
   toolchains to BuildParser names in the BuildSteps.
 * Enhance AbstractProcessStep to accept a IOutputParser to parse its output.
 * Remove AbstractMakeStep.
 * Set the appropriate Parsers in all classes deriving from AbstractProcessStep
   and append the ToolChain's parser to the parser chain.
 * Remove BuildParserFactories: There is no more need for them.
 * Remove constants used to identify the BuildParsers.
 * Clean up some names:
    * Replace stdOut with stdOutput.
    * Replace addToTaskWindow with addTask and addToOutputWindow with
      addOutput. Do this wherever it is not yet clear that this will end up
      in the Task/Output window.

Reviewed-by: dt