Add Primer3 run without sequence

Add Tools -> Primer -> Primer3

Here it will be possible to run Primer3 without sequence. Task is automatically set to check_primers without the ability to change. Region below is missing or disabled. On the Result Settings tab, "Save annotation(s) to" is replaced with "Path to file" (required in GenBank format, default in UGENE_DATA with the name primers.gb), Add to project (disabled by default) and Save immediately (default turned off). For an example, see the dialogue "Construct molecule". 

Tabs with exons and Posterior actions should be disabled. 

A sequence is created with primers: left 20N internal 20N right (need rev-compl)
If only one primer is given, then no Ns.
If there is none, we fail with an error. 

After calculation, primers are marked with annotations + qualifiers with data as for a regular primer.