[FEATURE] Add image-align-left and image-align-right

Update 2016-08-11: Submitted as PR https://github.com/benjaminkott/bootstrap_package/pull/367
## For `text with images` and `text with media` elements we have these four options for image alignment:

## This is fine as long as the images are large enough to fill the complete column:

## However, if the images are very small the only option you have at the moment is to display them horizontally centered:


This is a problem in real life for existing websites that have some small images and want to have them left aligned with the text for example. To address that problem I've created a patch that I'll send as a pull request.
## With that feature you have some more options in the alignment menu:

Namely there are additionally:
- above-left
- above-right
- below-left
- below-right

## For above-left (or below-left) you get:

## And for above-right (or below-right):

## And this is the real live usage: Display a little image left justified

## I will send a separate pull request.

The positioning is done with an extra class `image-align-left`or `image-align-right`in the `figure`-tag. In doing so the caption can be affected as well if somebody needs that. In less and css we're issuing a `left-margin: 0` or `right-margin:0` instead of the default `auto`.
## PS:

While investigating I came to the conclusion that it indeed doesn't make sense to have an alignment option `in text left` or `in text right` as that would require much more of specification to make sense in the bootstrap context.