Issue #28 Code comments are lost

Used ListRewrite.createCopyTarget() when copying node ranges.

ASTBuilder.java:
Added copyRange() which can return null + updated code making to avoid any problems with this null value.

Refactorings.java:
Added createCopyTarget(T first, T last) {

RemoveUnnecessaryLocalBeforeReturnRefactoring.java, VectorOldToNewAPIRefactoring.java:
Changed from ASTBuilder.copyAll() to ASTBuilder.copyRange().

RefactoringsTest.java:
Improved error reporting.
Issue #28 Code comments are lost

Do not lose comments when rewriting "if / else { if }" to "if / else if".
Updated samples and code.
Issue #28 Code comments are lost

Fixed more places by making proper use of JDT rewrite APIs.
Issue #28 Code comments are lost

ASTBuilder.java:
Changed copyExpr(Expression) to copySubtree(ASTNode).
Changed copyAll(List<Expression>) to copySubtrees(List<ASTNode>).