PDI-7426 - [PATCH] Subfolders for IMAP for Jobentry 'Get mails' and Transformation Step 'Email messages input'

junit tests added

new file:   engine/test-src/org/pentaho/di/job/entries/getpop/MailConnectionTest.java
PDI-7426 - [PATCH] Subfolders for IMAP for Jobentry 'Get mails' and transformation Step 'Email messages input'

patch applyed
PDI-7383 - Compatiblity Fix for "Get Mail from POP/IMAP" Job Entry and Transformation Step

added handling message attachment if not an instance of Multipart class