Introduce DependencyNotFoundException

 * it unifies the concept of missing dependency failure
 * it also stores the metadata about the missing dependency/artifact
   so that in can be later used in reporters and filters
Store additional metadata in BomDependencyNotFoundException

 * info about missing artifact and root dependency node can
   later be used in reporters and filters
Reporters now use metadata from *DependencyNotFoundException
Introduce the concept of ExceptionFilter + three basic implementations
Plug the exception filtering into the AppRunner
Store also validated artifact info in the DependencyNotFoundException

 * storing the artifact then enables matching on it in the
   exception filter (instead of the filename based matching so far)
 * BomDependencyNotFoundException is now subclass of
   DependencyNotFoundException as they share much and
   the "is a" relation holds.
Rename FileBasedExceptionFilter to FilenameBasedExceptionFilter

 * the new name better reflect the fact that the filter is
   operating on the file name not on the entire file
Create dependency-not-found filters from xml config
Create bom-dependency-not-found filters from xml config
Create filename based filters from xml config
Add filter examples into sample wolf config
Fix the dependency exceptions squashing in surefire reporter + add test cases

 * the reporter was broken due to the recent changes in how the dependency
   exceptions are reported. Now all exceptions pointing to same missing
   artifact are squashed into single test failure.
 * the DependencyNotFoundException now creates default DependencyNode under
   the good (from the validated artifact) if none specified. The reporting
   and generally handling the exception is now much easier.
Clean-up the exception filters loading

 * all the filters are registered as beans, so there
   is no need for the additional method gather* method
Log ignored exceptions and details about the exception filters being applied
Add basic info about the filter configuration into the README
Merge pull request #13 from psiroky/exception-filter

Exception filters + few other fixes/imporovements