Fixes for reading/updating system variables
XMLParser : Load external XML with auto switch to default if file not exists

To use your own customized checklist, create an xml file with the name
of checklist_ext.xml and put into SD0/DroidPlanner/Checklist/

the parser will automatically fallback to default xml from resource if
the external file is not found
RowItemChangeListener : simplifiled interface

Remove individual Row Type listener
Add a unified listener for all Row Types
get_SysTag() is used to differentiate different type
RowItemChangeListener : OnRowItemGetData

Add a new listener to be called everytime RowItem need to read data
from the system
Refactoring : unified get/setSystemData

move the getSystemData from individual rowitem into listener type of
implementation.
DialogBox will supply the information when the Row requires data to be
read from the system
CheckListAdapter : Auto Expand

Auto Expand if there are items not check and number of checked items
are below number of mandatory items
CheckListAdapter : AutoCollapse

Auto collapse when all check itmes are checked

Default checklist is now proper.
CheckListSysLink : Move System link to class

All system related data (get/set) are now move into a class.
CheckListSysLink: SYS_DEF_ALT Fix

SYS_DEF_ALT is now working
Merge pull request #379 from azrin1972/CheckList-Fixes

Check list fixes & enhancements