Fix bool column behavior in Oracle queries

[maio]

Fix how bool values are sent to Oracle DB. Previously BooleanColumnType
didn't do any conversion so real boolean value did reach JDBC and it has
been converted to numeric value of 0 or 1.

This behavior is not correct as bool columns in Exposed are CHAR(1) in Oracle.
We need to pass bool as a string instead of a number otherwise Oracle will not use
indexes when such column is used in WHERE clause.

Example:

create table foo (boolColumn char(1));
create index foo_idx on foo (boolColumn);

With numeric value:

select 1 from foo where boolColumn = 1;    // results in full table scan (ignores foo_idx)

--------------------------------------------------------------------------
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |      |     1 |     3 |     2   (0)| 00:00:01 |
|*  1 |  TABLE ACCESS FULL| FOO  |     1 |     3 |     2   (0)| 00:00:01 |
--------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

"   1 - filter(TO_NUMBER(""BOOLCOLUMN"")=1)"

With string value:

select 1 from foo where boolColumn = '1';  // correctly uses foo_idx

----------------------------------------------------------------------------
| Id  | Operation        | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------
|   0 | SELECT STATEMENT |         |     1 |     3 |     1   (0)| 00:00:01 |
|*  1 |  INDEX RANGE SCAN| FOO_IDX |     1 |     3 |     1   (0)| 00:00:01 |
----------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

"   1 - access(""BOOLCOLUMN""='1')"