Add enzyme's overhangs and the corresponding filter

Each enzyme could have a certain types of overhangs (sometimes one site has several of them):

• Blunt - the cut is located in the middle of the site.
  
• Sticky - the cut is locate anywhere but the middle of the site.
  
• Nondegenerate sticky - the save as previous, but the overhang between cuts has only A, C, G or T  (no extended) symbols.
• 5' - the cut of the forward strand is to the left of the cut of the reverse-complementary strand.
  
• 3' - the cut of the forward strand is to the right of the cut of the reverse-complementary strand (see sticky image).
• Single-strand nick - cut only on one strand (not sure, that our database has this type). They are not just "Sticky"
  

Also we need to add two mixed points:

• Blunt and sticky. If there are no "Single-strand nick" in our database, it will be "Blunt and sticky (Any)".
• Blunt and nondegenerate sticky.