Add the ability to edit HSLFPictureData contents

Add the ability to edit HSLFPictureData contents

Pictures can now be edited by calling HSLFPictureData#setData(byte[]). The byte[] should contain the image data as an image viewer might read it.

To enable this functionality, a tighter coupling between the EscherBSERecords of the slideshow and the HSLFPictureData was required. This ensures that changes in image data size are accurately recorded in the records.

In the course of coupling the records and the HSLFPictureData, various scenarios arose where a mapping of records to pictures was non-trivial. Accordingly, the HSLFSlideShowImpl#matchPicturesAndRecords(...) function was added to perform a more sophisticated matching pass. This function is heavily exercised by org.apache.poi.hslf.usermodel.TestBugs.testFile[5] and PPTX2PNG.render[2], as well as the new TestPictures#testSlideshowWithIncorrectOffsets().

Closes #225

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1887017 13f79535-47bb-0310-9956-ffa450edef68