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.*
zss-577, test case and fine tune formula expression to allow multiple areaRefs inside it.
zss-577, support (A1,B1,C1) in parse and evaluation, but didn't handle shift,transpose,move,shrink,extend,renameSheet yet
refix zss-591 for chart loop evaluation
zss-577 - suport multiple area shift/transpose
zss-577 support multiple area , move (shrink,extend), renameSheet(deleteSheet)
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
add javadoc for org.zkoss.zss.model.*, org.zkoss.zss.model.chart, org.zkoss.zss.model.util
* rename class
- InvalidateFormulaException -> InvalidFormulaException
- InvalidateModelOpException -> InvalidModelOpException
all methods and variables use gridelines. (appended with s)
fix testcase for data-format, currently, we don't support to guess/transfer user's format automatically.
Merge branch 'origin/3.0'

Conflicts:
	zss.test/src/test/java/org/zkoss/zss/api/impl/DateInputTest.java
refine format-engine api
Merge branch 'origin/3.5'