LUN-1192 : Remove default space for image plugin
- add 15px margin to the left or right only when image is floated left or right
- make sure margin is added even when alignment is set from text plugin
- let the user overwite the default margin in any case
- allow 0 for vertical and horizontal space
Merge pull request #25 from pbs/LUN-1192

LUN-1192 : Remove default space for image plugin