Change BrowserSim error message when it cannot be run on Windows with JRE 7u6/7u7

Please see the parent issue JBIDE-12467 for full description of the problem.

This bug is about the following changes witch fix this problem partially:

1. BrowserSim launcher should try to run BrowserSim with JDK 7 (not JRE), if it is available through the 'eclipse.vm' variable.
2. BrowserSim should show the following message (a more precise) if the error appears:
   

4QAs: please ensure that:

1. BrowserSim shows new error message if Eclipse is run with JRE 7u6 or JRE 7u7.
2. BrowserSim is working properly if Eclipse is run with JDK 7u7.
3. BrowserSim is working if Eclipse is run with JRE 7u5 and below.

Please use -vm param in eclipse.ini to specify JVM.