Add some grace for overlapping synteny blocks

[lcoombe]

• There is code in ntSynt to print a warning if an overlap is detected between synteny blocks
• But, when I looked at examples, they were generally very small (<5bp) overlaps
  • I don't think this is a concern
• The intention of the warning is to have logic in there to identify when synteny blocks have very large overlaps (which could indicate an issue)
  • I thought that having these warnings printing when there really wasn't any concern confusing
• So, implemented a check where the warning is only printed out if the overlap is large (over -z, default 500bp)