Add a class in orbisgis core to convert a layer into image stream
Export map editor tool in Orbisgis view
Add DPI input
Add icon and fix layout issues.

I redid the InputPanel class's layout using MigLayout. I also removed
the grouping since it wasn't used anywhere and made the code rather
complicated to read.
Add confirmation for overwrite
Do some translations
improves javadoc and adds a default description in new Rules
Adds Description management in the PnlRule.
Description are made of a title and/or abstract associated to a Locale.
We now have a ComboBox managing the locale and updating text area fields
that can be used to change the abstract and title.
Improves the content of the combo box.
It is now a WideComboBox that relies on ContainerItem instances.
The abstract text area is now in a JScrollPane.
We now remove titles and abstracts that are empty or null.
Adds description in Style and description management in PnlStyle
adds french translation for the keys I added
Merge pull request #519 from nicolas-f/feature/export-mapeditor

MapEditor export image tool

* Create MapImageWriter, taken from WMS server in order to easily convert a layer into an image stream.
* Add a new tool in MapEditor to export the current rendered map into an external PNG or TIFF file.
adds translations
Merge remote-tracking branch 'upstream/master' into 486-merge

Conflicts:
	orbisgis-view/src/main/resources/org/orbisgis/view/translation/language/fr.po
Improves translation everywhere it was possible for me
Replace X11, headless exception by a test and log.trace
Merge pull request #527 from nicolas-f/fix/headless-error

Replace X11, headless exception by a test and log.trace
Fix typos in the javadoc