OPENDJ-3527 OPENDJ-3531 OPENDJ-1633 Fix tools bootstrap

Cleanup in the way we mange to compute OPENDJ_JAVA_BIN and OPENDJ_JAVA_ARGS environment variable for our tools.

Removes lib/set-java-home and lib\set-java-home.bat
Now lib/_script_util[.sh | .bat] use the following order to determine java home:
    * Use OPENDJ_JAVA_BIN if exists and points to an existing file
    * Use OPENDJ_JAVA_HOME if exists and OPENDJ_JAVA_HOME/bin/java[.exe] is an existing file
    * **NEW** read the property 'SCRIPT_NAME.java-home' in config/java.properties file and uses it if the PROPERTY_VALUE/bin/java[.exe] is an existing file
    * **NEW** read the property 'default.java-home' in config/java.properties file and uses it if the PROPERTY_VALUE/bin/java[.exe] is an existing file
    * Otherwise try to call java command as before
    * If no java has been found, prints an error message (which has been adapted by this change)

Replaces the 'Java Settings' panel by a message which indicates to the user that he have to modify the java.properties file to update runtime settings.
Removes the dsjavaproperties tool since it is now useless
Also fix OPENDJ-3531 by removing support of OPENDS_JAVA_* legacy environment variables
Also fix OPENDJ-1633 by adding an explicit --offline arguments to all server tools which have offline mode.