junit: don't detect custom scope in IDE, leave it for ServiceLoader: if find custom engines, then try to start with junit 5

Output is cleaned in CompilationContextImpl.cleanOutput. Cleaning it here may cause problems if 'compileModules' is invoked several times.

Check gui availability with environment variable on Linux

IDEA-170613 Patch Update: IDEA doesn't start after update with "No JDK found" message
IDEA-167664 intellij cannot find java on linux because it looks into the wrong directory
IDEA-156867 idea.bat misunderstands quoted IDEA_JDK path

According to http://stackoverflow.com/questions/10824178/how-do-you-redirect-standard-input-to-a-file-in-the-windows-command-line: "FINDSTR will hang indefinitely on XP and Windows 7 if reading redirected input and the last line does not end with <LF>"

In Groovy forward references to instance fields from field initializers are allowed but return default values of corresponding types, so actually old system properties were ignored.

don't bother kb on his birthday

Now both options (when unchecked) only disable warning and batch-mode replacement, but the action is still available as an intention.