This commit converts the build to a Gradle based build. It also setup sonar
integration at https://sonar.springsource.org/dashboard/index/11620
Currently tests in the samples fail on the CI server and are disabled. The
tests were not enabled for the maven based build either.
Issue: LDAP-251
DirContextAdapter#setDn() now throws IllegalStateException if setDn is called on an
instance in update mode (this was previously silently ignored)
Fixed problem in LdapTreeBuilder caused by the new behaviour of DN in DirContextAdapter
(i.e. that the actual DN instance of the DirContextAdapter is no longer returned by
getDn()).