Improved BSN aligner description regarding assumptions/specifications and design descisions. Added dp_validate_crc and dp_validate_bsn_at_sync.

Updated SDP timing description and BSN aligner selection to almost final state. Updated other txt files at some points.

changed usage of user_components.ipx file, now a copy from git is places in each [version]/ip/altera/ directory

Add LOFAR2.0 directory for designs and doc. Use initial empty readme.txt file becasue Git does not add empty dir.