Include mandatory statement for leafs

[PrathibaJee]

As per TR-532 mapping guideline , for leafs , if mandatory statement is 1 , then mandatory sub statement shall be true.

As per RFC 6020 section 7.6.1 ,

Since we have default values included for all the attributes in the already provided technology specific modules, we are planning to use the following condition for including mandatory substatement,
(if multiplicity = 1 in UML) AND (no default value defined) => (then mandatory statement to be put into YANG)

To support this change, the following needs to be modified,

• models\tools\xmi-to-yang\src\main\resources\parser\processors.js to support Obj2Yang
• models\tools\xmi-to-yang\src\main\resources\generator\yangprocessors.js to buildChild
• models\tools\xmi-to-yang\src\main\resources\model\OwnedAttribute.js to store lowerValue parameter in the store
• models\tools\xmi-to-yang\src\main\resources\model\yang\leaf.js to support writeNode(to print the mandatory statement in the Yang)