[bpmn2-modeler-dev] Target Platform improvements

[Cristiano Gavião <cvgaviao@xxxxxxxxx>]

Hi guys,

I got happy to see that bpmn2-modeler is part of eclipse now, and happy 
to see lot of improvements since last time I worked with the editor from 
github. Congratulations to all team.

But I got some problems installing the plugin from the created update site.

After clone the source, I saw some outdated things within the tycho 
build, mainly in the org.eclipse.bpmn2.modeler.updatesite.feature, that 
is not creating the site.zip properly. I got some difficult to create a 
target platform properly inside the IDE, too.

So I would like to propose some improvements:

- move the site project to a p2 repository project instead;
  Besides, using a P2 repo let us to create Composite Repositories, so 
we can facilitate the installation of the plugin and all dependencies 
using only one p2 address.

- create a target platform description project (containing one target 
file per eclipse version, helios/indigo/juno) to easy creation of the 
dev environment at IDE; actually, this is better than work with 
repositories at pom, because it will be cases where we need to build 
with different dependencies components versions depending which IDE 
version (for example: EMF, 2.7 at Indigo and 2.8 at Juno).

- add a juno profile at main pom;


cheers

Cristiano