Oracle updates and benchmark fixes

As already discussed with Djellel, I have worked with the code and fixed some things for Oracle databases. I noticed that some of the code for Oracle is untested and needed some work.

In particular, I have fixed the following issues:

* Updated Oracle JDBC driver to current version (so it works with the latest Oracle release)
* Small fix to TPCC workload examples
* More fixes for the Oracle Wikipedia workload (quoted names and empty string handling)

In detail, the following changes were made:

* 344a5a9b275ea8197b9e30e8fc36ff5d96383abc
I tested the code with the latest Oracle database release 12.1.0.1 and received ORA-28040 errors (which usually indicate an old client version). This commit replaces the old ojdbc5.jar (Oracle 11g) and ojdbc14.jar (Oracle 10g) files with the latest OJDBC6 drivers downloaded from Oracle.

* e6aaaa1557d63ba7f8b49cb3d71daea3164b4ca1
Small commit that fixes the missing `<dbtype>` tag in the TPCC benchmark example config file.

* 3adbee7af805bdb7addb74e42c89ed0044f395aa
This commit fixes the Wikipedia benchmark for Oracle databases.
    - Fixed DDL script, had some wrong field sizes and wrong table names (for example "user" instead of "useracct")
    - Oracle handles quoted object identifiers differently than other RDBMS. For example, 'customer' and '"customer"' are not the same tables. In the current workaround, the INSERT statements are re-generated if the `WikipediaLoader` is run with Oracle.
    - Also, Oracle handles an empty string ("") as a NULL value. Some values are generated with a random length (RNG), which can also generate a string of length 0. Since "" is treated as a NULL value, this violates the NOT NULL constraint on the columns. The workaround adds `+1` to the length of some randomly generated values.

* 1928bd4813950efb873a90e8987a7f6f64e2ec7d
Interestingly, git handles "wikipedia-oracle-ddl.sql" as a binary file (probably because it contains some non-printable characters). This commit re-writes the file without some special characters. Nothing else was changed.

All changes were tested with the latest Oracle release 12.1.0.1. Please let me know if you have any questions or concerns.