fix #2579 add AbstractConfigHelper

...n/java/org/codelibs/fess/helper/AbstractConfigHelper.java

src/main/java/org/codelibs/fess/helper/KeyMatchHelper.java

src/main/java/org/codelibs/fess/helper/LabelTypeHelper.java

...main/java/org/codelibs/fess/helper/PathMappingHelper.java

...n/java/org/codelibs/fess/helper/RelatedContentHelper.java

...ain/java/org/codelibs/fess/helper/RelatedQueryHelper.java

src/main/java/org/codelibs/fess/helper/SystemHelper.java

src/main/java/org/codelibs/fess/job/JobExecutor.java