Converted Sharpshooter's Deadeye ability to Headshot from the first game

Converts the Sharpshooter's Deadeye ability to Headshot from the first game.

Replaces Deadeye with the headshot skills of the old XCOM sniper.

It's still called Deadeye because mechs don't really have heads, but it's like Headshot from XCOM Enemy Within.

Details:

• 5% target penalty. XCOM 2 Sniper hits 91 targets, plus 10%-ish from PCS, 15% from Advantage Range, +10% from Steady Hand or +20% from Aim for ~125% base target. Tracker added 10% optional. The XCOM 1 sniper has a maximum range of 105 targets, +10 targets from target, +10 from Damn Good Ground, and a final range of about 125. Executioner +10%. If the XCOM 2 version takes a 5% hit, that's about it.
• Ignore eating grass. Making this skill ideal for opening Salvos or finishing off enemies.
• Maintain Deadeye's 3-turn cooldown. This forces you to choose carefully when preparing for a critical hit.
• Ignore typical squadsight critical chance penalty. It looks thematically appropriate, but more importantly, is a more fluid factor for each range, for everyone.
• 2/2/4 extra damage, allowing snipers to do almost double damage. The expected critical damage numbers for the three levels are 9, 12, and 17 respectively. 12 gives you a one-shot shot, but not a berserker. 17 points of damage will let you one-shot the most basic enemies, but the difficulty on Commander won't let you catapult the Guardians, Andromedas, Gatekeepers, and Limbs.
• To adjust these numbers manually, edit XComModDeadeyeToHeadshot.ini.

compatibility:

• This only modifies Deadeye's abilities, so as long as no other mod overrides class X2Effect_DeadeyeDamage, you'll be good.
• This mod can be safely removed. Removal simply returns Deadeye's ability to its vanilla form.
• This mod deals +2 critical damage to the Unconventional, Magnetic or Beam weapon classes.