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.