Issue #50 New refactoring - remove empty comments

Removed empty comments and Eclipse generated TODO comments.

ASTCommentRewriter.java: ADDED

Refactorings.java, AutoRefactorHandler.java:
Added support for removing comments.

RemoveEmptyCommentsRefactoring.java:
Completed the existing code, in particular for Eclipse generated TODO comments.

RemoveEmptyCommentsSample.java:
Completed the samples with more test cases and Eclipse generated TODO comments.