CustomAnalyzer ctor to set AnalyzerBase.Type

By providing a ctor that sets the Type property users will not need to remember
to set the type property manually.

Removing the default ctor would be a breaking change.  Marking it obsolete
should lead most people to "the pit of success".
Remove obsolete attribute
Merge pull request #431 from sschlesier/CustomAnalyzer-ctor

CustomAnalyzer ctor to set AnalyzerBase.Type