This commit introduces the 'handler' package under 'de.eudx.data' to handle the cleaning and processing
of incomplete records within a dataset, in correspondence with issue Samyssmile#23.

Changes Made:
- Added 'handler' package under 'de.edux.data'
- Introduced 'EIncompleteRecordsHandlerStratetgy' enum with the constans:
  DO_NOT_HANDLE, DROP_RECORDS, FILL_RECORDS_WITH_AVERAGE
- Introduced 'IIncompleteRecordsHandler' interface
- Implemented 'DropIncompleteRecordsHandler' class
- Implemented 'AverageFillIncompleteRecordsHandler' class
- Implemented 'DoNotHandleIncompleteRecords' class because
  of DataProcessorTest.testLoadDataWithoutNormalizationAndShuffling()
- Started to write the tests for the above mentioned classes and their methods
- Revired the existing codebase to be compatible with the new enum

…ecordsHandlers

…m for Enhanced Data Handling

Implemented the ImputationStrategy enum with constants of average and mode and the corresponding classes.

Average imputation throwed RuntimeException beacuse the condition in the isDigit() method
was returning false for blank values. Fixed with an or operator.