Oracle XE 18.3 support

[maxsatula]

Apparently, need to replace https://edelivery.oracle.com/akam/otn/linux/ with https://edelivery.oracle.com/otn/linux/ (remove "/akam") in download.js

Secondly, a different default for ORACLE_FILE=oracle18c/xe/oracle-database-xe-18c-1.0-1.x86_64.rpm

Also, it is downloaded as .rpm, not as .zip anymore,

Not figured out yet, why sometimes download fails sometimes not, perhaps Oracle website has some limits set.