3.1.1 release - Githubissues

[x] Create a branch for the release if it does not exist
[x] Update the branch of the build status in README.md (3.1)
[x] Build the package with the command mvn install -P sign,upload,archive (3.1)
[x] Tag to the release on git with the command git tag -s v3.1.1 HEAD (3.1)
[x] Push changes to GitHub with the command git push upstream 3.1 and git push upstream --tags (3.1)
[x] Create a new draft release as MakeGood 3.1.1 (stable) (GitHub)
[x] Upload the update site zip file /path/to/makegood/com.piece_framework.makegood.p2repository/target/makegood-3.1.1-SNAPSHOT-update-site.zip
[x] Rename the uploaded file to makegood-3.1.1-update-site.zip
[x] Write the description of the release
[x] Publish the release
[x] Update wiki pages (Home and Contributors)
[x] Update the version of the pom.xml of each plugin from 3.1.1-SNAPSHOT to 3.1.2-SNAPSHOT (master)
[x] Update the version of MANIFEST.MF of each plugin from 3.1.1.qualifier to 3.1.2.qualifier (master)
[x] Merge v3.1.1 into master with the command git merge v3.1.1 (master)
[x] Push changes to GitHub with the command git push upstream master (master)
[x] Tweet the release
[x] Update information on Eclipse Marketplace

piece / makegood