Improved navigation interface, added next() method

[rsoika]

This is a smaller improvement of the org.odftoolkit.odfdom.incubator.search.Navigation Interface.

Using this feature in my own project I recognized that the TextNavigation was not working correctly - especially in case the search pattern occur multiple times in one document or paragraph.

The following example shows how to replace all matches of a regex with a text using the new implementation:

	private void replaceODFTextFragment(OdfTextDocument doc, String pattern, String replace)
			throws InvalidNavigationException {
		try {			
			TextNavigation searchPattern = new TextNavigation(pattern, doc);
			while (searchPattern.hasNext()) {
				OdfElement element = searchPattern.next(); //.getCurrentItem().getElement();
				String text=element.getTextContent();
				logger.info(" Current Item Text="+text);
				element.setTextContent(replace);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

The method TextNavigation.next() is new and a convenient method for getCurrentItem().getElement();

An important bugfix is in the method setCurrentTextAndGetIndex. This method runs in a outOfBounds Exception in case the pattern length was equals to the replacement text length. This is now also fixed.

I have tested the new code in my own project and it works now perfect - even with text in embedded table cells.

[svanteschubert]

Thank you, Ralph, for this patch fixing the search functionality.
As it was broken earlier the renaming (API change) should not matter to me.