document abstract source code analyzer, fixes #1724

Author: Lubos Kosco

src/org/opensolaris/opengrok/analysis/plain/AbstractSourceCodeAnalyzer.java

@@ -36,6 +36,20 @@
 /**
  *
  * @author Lubos Kosco
+ * 
+ * This class should abstract all analysers that deal with source code.
+ * Source code is specific that it has definitions and references.
+ * Source code has custom xref generators, depending on symbols.
+ * This class should mark the classes that can provide defs and refs.
+ * NOTE: SymbolTokenizer gets set for #1376 in PlainAnalyzer::analyze
+ * and not part of this class anymore due to changes in lucene 6 .
+ * 
+ * Anything shared just for source code analyzers should be here,
+ * also all interfaces for source code analyzer should start here.
+ * 
+ * Any child is forced to provide necessary xref and symbol tokenizers,
+ * if it fails to do so it will automatically behave like PlainAnalyzer.
+ * 
  */
 public abstract class AbstractSourceCodeAnalyzer extends PlainAnalyzer {