Remove patches for Xtend bugs(issue #109)
Avoid errors in the model inferrer.
Add missing return types.
Update the model inferred according to Xtext 2.7.0.
First version of the content assist (issue #123).
Move to Xtext 2.7.0

Note that because the version 2.7.0 is not yet available on Maven
Central, we still using the version 2.6.1 for compiling on the CLI.
Apply the developer conventions to the Eclipse plugin.
Ficing the invalid name of the target platform in the root pom.
Update dependencies of the Eclipse elements.
Fixing the content assist bug (issue #109)
Revert 802c443c54dd40a05c400718dea65fae81537009 for Xtext 2.6.2 (issue #116).
Update Eclipse plugin dependencies for Xtext 2.6.2 (issue #116).
Rename the module 'io.sarl.sdk' to 'io.sarl.maven.sdk' (issue #132)
REname the Maven parent modules (issue #133).
Add missed version for the Maven SDK (issue #132).
Remove README files for the upgrade process.