improve PBT UI & handling for lineup changes

[frank-weinberg]

• Unless no skater is selected yet, the row of buttons is hidden behind an "Edit Lineup" button.
• In addition the dialog doesn't close on clock start when no skater is selected because most likely the operator will want to select the skater at this point.
• All penalty code/count display and add buttons are hidden when no skater is selected as they won't work anyway.
• The "Substitute" button now reads "Select Skater" and is orange when no skater is selected for the position.
• It's no longer possible to assign multiple clocks to the same position in parallel
• Assigning an initial penalty now also works when the skater is selected after the clock is assigned to a position.

closes #733