wisemapping init script: add a java_opts parameter used into the init script template.
wisemapping init script: use wisemapping_dir in the init script template.
wisemapping init script: protect START_CMD with simple quotes.
wisemapping: fix default value for java_opts.
wisemapping: document java_opts.
wisemapping: export JAVA_HOME if java_home parameter is set.
wisemapping: document java_home, default to undef.