Geopal: lint
Ed: compute boundary shape

For the moment we compute convex shape since concav is only for postgis
2+ and it's not yet available in debian stable
Jormun: call other overlapped kraken if no solution

if no solution found and other overlapped kraken are available we call
them
Jormun: add integration tests
Jormun: add a debug mode

in debug we add some info to the response
Geopal: correction after review
Merge pull request #531 from antoine-de/convex_shape

Convex shape