Views toolbar in the sequence view

The following modifications are required:

1. Divide the sequence view toolbar into two toolbars: "Standard" and "Views visibility".

2. Move all buttons from the current toolbar to the "Standard" one, except:

• The green arrow "Toggle views" button
• Circular view button.

3. Draw icons for views:

• Sequence overview.
• Zoom view.
• Details view.

4. Add the following checkable buttons to the "Views visibility" toolbar:

• Sequence overview
• Zoom view
• Details view
• Chromatogram view - this button should be available only if the sequence has association with a chromatogram object.
• Circular view - this button should be available for nucleotide sequences only!

Additional note for testing:

• Consider the case when a sequence alphabet is modified from nucleotide to amino acid. Hide the button in this case.