Find definition for start/end tag element

[angelozerr]

When an XML element contains a big content, it's hard to jump from the start tag element to end tag element and vice versa:

To fix this problem it should be good to provide a find definition for start/end tag element like this demo:

[angelozerr]

@fbricon I'm sorry I have merged this issue although I didn't want to do that -( I think this issue is simply and there are a lot of tests which covers this feature. If you wish I remove this commit, please tell me.