fix #2554 use environment variables in parameters

src/main/java/org/codelibs/fess/ds/AbstractDataStore.java

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

.../java/org/codelibs/fess/mylasta/direction/FessConfig.java

src/main/resources/fess_config.properties

src/test/java/org/codelibs/fess/helper/SystemHelperTest.java