update javadoc for org.zkoss.zss.range.*
add maven-checkstyle-plugin and its configuration
add @since 3.5.0
fix zss-585.
zss \ 6 places \ DateFormatSymbols.getInstance() -->
new DateFormatSymbols()
Merge branch '3.0' for ZSS-585

Conflicts:
	zssmodel/src/org/zkoss/zss/model/impl/sys/FullMonthData.java
	zssmodel/src/org/zkoss/zss/range/impl/autofill/ShortMonthData.java
	zssmodel/src/org/zkoss/zss/range/impl/autofill/ShortWeekData.java
write javadoc for org.zkoss.zss.model.*
Merge branch 'origin/3.5'

Conflicts:
	zssmodel/src/org/zkoss/zss/range/SRange.java
zss-577/zss 606 , release note and re-add testcase for