toggle alignment of images by click

[issue #120](https://github.com/litewrite/litewrite/issues/120)
Probably this code going to be rewritten, because method I used is deprecated since jQuery 1.9
Currently it (should) works.

I suggest to try it out and decide if we actually want GUI for this, because after testing this feature I feel like it would be better with GUI: more convinient, more elegant.