add basic infrastructure to handle other / multiple files extensions for specification documents
pull changes from jacek-ratzinger/master

* remotes/jacek-ratzinger/master:
  rename project Concordion.Integration.NUnit to Concordion.NUnit
  fix loading of config files: use Assembly.CodeBase instead of Assembly.Location -> all Spec tests pass with NUnit  -> all Spec tests pass
  change TargetFrameworkVersion to 4.0 in order to be able to run Concordion specs with NUnit 2.6.3
  change Addin name to better reflect intention with NUnit attribute "RequiredAddin"
  finish implementation of boolean mapping: get tests green
  add specification with examples: for new bool string handling
  make tests pass with new Checker infrastructure
  add basic implementation for new boolean matching
cleanup after merge of jacek-ratzinger/master in preperation for future commits
Multiple files extensions for specification
Better error handling for testfiles with no specification
switch TestRig to new Extension architecture
clean-up; remove obsolete code
switch to IAssertTrueListener and IAssertFalseListener
switch to IDocumentParsingListener, ISpecificationProcessingListener, and IConcordionBuildListener
finish JavaScript extension
finish CSS extension
finish ResourceExtension
finish CommandExtension
don't commit csproj.user files
prepare FileSuffixExtensionsTest - pull changes of Elvira on SpecificationLocator
improve stability of NUnit test execution
finish ExtensionConfigurationTest: implement Extension / Extensions attributes and configurations to load extensions
fix configuration example for extensions
restructure Extension specifications and add overview page
finish Listeners and Extensions