Clean up .classpath files

Some .classpath files still contain references to SCALA_CONTAINER and
SCALA_COMPILER_CONTAINER which are not needed anymore. Furthermore
sdt.core explicitly references JavaSE-1.6 as its runtime environment
which shoudn't be included either because this doesn't allow a JRE
independent build.
Fix warning about adapted argument list

This warning became an error in 2.11 since scala/scala#3260, when
-Xfuture is enabled.
Updating the License to the latest Scala License.
Merge pull request #626 from sschaef/t-cleanup-classpath-files

Clean up .classpath files
Merge pull request #631 from sschaef/t-fix-last-remaining-adapted-arg

Fix warning about adapted argument list
Merge pull request #632 from huitseeker/issue/LicenseUpdate

Updating the License to the latest Scala License.
Only ask for diagnostics at first install and if heap is not sufficient.

Added PreferenceStore wrapper allowing to get options.

Fixes #1001113
Removing the custom "non-idiomatic" eclipse preferences wrapper. And adding automatic editing of eclipse.ini.

Fixes after review.
Merge pull request #628 from huitseeker/issue/1001113

Only ask for diagnostics at first install and if heap is not sufficient.