Improve "Probe and SAI" visualization (SAI-vis)

[westram]

Issues:

• display of SAI-vis is incredibly slow (with a few thousands of probes it's already unusable)
• probe selected in SAI-vis and probe selected in match results should be coupled

Improvements:

Display:

• do not always (re-)display SAI-vis for all probes
• instead use scroll-offset (similar to matrix-display in arb_dist) and
  only (re-)display what fits into current viewport
• always keep header visible

Coupling:

• (fix #746 before)
• select probe in SAI-Viz ⇒ write to probe match AWAR
• changing probe match AWAR shall select and scroll to probe in SAI-vis

Interaction:

• clicking onto displayed sequence should set cursor position to clicked base position
  (using AWAR AWAR_SET_CURSOR_POSITION)

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requires: #746