IDE don't save Java compiler preferences after stop workspace

[ddementieva]

Steps to reproduce:

1. Go to: Profile -> Preferences -> Java Compiler
2. Set value "error" for properties: "Value of local variable is not used": .
3. Click "Save" button.
4. Create new project from Spring sample.
5. Open project and wait until IDE resolves dependensies.
6. Open GreetingController class from created project.
7. Add code "int l = 0;" to the method "handleRequest";
   IDE should create error marker for added code line.
8. Go to machine perspective.
9. Select Machine -> stop
10. Refresh page with IDE. Wait until ide will be initialized.
11. Open Spring project.
12. Open GreetingController class.
    Actual result: line with code "int l = 0;" contains warning marker, because IDE didn't store java compiler preference and got default preferences.
    Expected result: line with code "int l = 0;" sholud contains error marker