Move and Size Tails of a multi-tail arrow about ketcher

[ivanmaslow]

During exploratory preview testing on the nightly environment (5107-move-size-head-tails) some issues are found, need to be fixed:

• Can't remove middle tail;
• Can move tail to any place on spine if selection tool is used;
• When moving down the top tail, it stops 0.35 before head but should stop 0.15
• Multiple issues with rounding of coordinates for tails, issues for cases when there are no free spaces for moving tail;
• Can't put tail to 0.35 before the bottom tail, it returns back;
• Console issue when image is added to Canvas;

[ivanmaslow]

Points above are fixed and verified on Nightly environment (5057-hover-selection):

• Middle tail can be removed:
  
• Tails can be moved when the selection tool is used:
  
• When moving down the top tail, it stops 0.15 before head:
  
• Issues for cases when there are no free spaces for moving tail related to rounding - fixed, no errors are in console;
• Tail can be put to 0.35 before the bottom tail:
  
• Console issue when image is added to Canvas - fixed, no error are in console;