Refactor fleet missions' code | Part 04 | Morale modifiers calculation

[mdziekon]

Summary:

Currently there are several places where morale-related modifiers are calculated manually for each attacker and defender, also duplicated in several files. All of these modifiers are applied identically, therefore they should be calculated using a shared utility function.

Changelog:

• Extract morale combat modifiers calculating function
• Use the new combat updating functions in attacks handling functions:
  • Regular attack
  • Group attack (ACS)
  • Moon destruction
• Extract morale pillage modifiers calculating function
• Use the new pillage updating functions in attacks handling functions:
  • Regular attack
  • Group attack (ACS)
  • Moon destruction
• Bugfix: when sending a united attack by yourself (only one attacker), apply morale BONUS when pillaging

Related issues or PRs:

• Refactor fleet missions' code #91