Issue #32 Add a CFG (Control Flow Graph) builder

Supported a simple case with IfElseIfSample.java.

IfElseIfSample.java: ADDED
Test sample.

IfElseIfSample.dot: ADDED
Expected test outcome.

CFGBasicBlock.java, CFGBuilder.java, CFGEdge.java, AutoRefactorHandler.java:
Added the supporting changes.
Simplified the code where possible.

CFGEdgeBuilder.java, CFGDotPrinter.java, CodePathCollector.java: ADDED

ASTHelper.java:
Added getNextStatement().

CFGASTVisitor.java: REMOVED
Added files to .gitignore
Added some ideas for remove empty comments refactoring