PDI-9937 - As an ETL developer, I'd like the check if a folder is empty step short-circuit as soon as a file is found

What was done:
1) added a new exception type
2) changed the way iteration is done in TextFileSelector (Kettle source files)
3) added a new exception handling logic
PDI-10764 - Fail on importing from existing ktr file while using oracle db as repository.

The problem is that column type for oracle is CLOB, but the column is used
in where sectio of queries as a normal varchar2 whhich does not work.
So I changed the code creating repository to limit NAMESPACE NAME to 2000
charatcers instead of 2000

What was done:
1) changed the way we init the repository
2) implemented getMaxVARCHARLength() for Oracle and MSSQL
3) changed implementation of corresponding getFieldDefinition methods to
use member getter instead of hardcoded value

What was done later:
1) changed the way we select type length
Refactor the class to allow unit testing
[PDI-9815] Show appropriate err msg if technical key is null
PDI-10764 - Fail on importing from existing ktr file while using oracle db as repository.

WHat was done
1) changed the way value is selected
Merge pull request #159 from kolinus/PDI-9937

PDI-9937 - As an ETL developer, I'd like the check if a folder is empty ...
Merge pull request #167 from askdzmitry/PDI-9815

[PDI-9815] 'Dimension lookup/update' step causes error: "Unable to retrieve data type of return fields because of an unexpected error" with Vertica
Merge pull request #166 from kolinus/PDI-10764

PDI-10764 - Fail on importing from existing ktr file while using oracle db as repository.
Merge remote-tracking branch 'upstream/master'