Turn Details Overlay on Boardview

[pakfront]

This displays an optional overlay on the board view that gives the specific Moves or Actions a unit will do when the turn is Done.
This is very helpful in understanding what will happen in a turn, and makes debugging turn behavior a bit easier.

In the Move overlay, any set of moves that require a PSR get a * appended to their entry. Any illegal moves, such as moves beyond MP limit, are greyed out. There are also unicode icons for some move actions.
This fixes #4486

I optimized and centralized the code to calculate and itemize the user displayed ToHits for this feature and AttackSprites. This fixes #4501.
An important change - in FiringDisplay I switched the order of adding attacks to Game and to the local Log so that the Game add is first. This fixes the issues where the ToHit mods displayed to the user were not calculated correctly when the attack was first added. This should have not break anything, it is more correct and when the ToHits are sent to the server, they go through another recalc pass that verifies the values.

There are cases where the display differs from the actual results. Without considerable and possibly disruptivework, these are unavoidable due to the way MegaMek works:

• In Move phase, it will display the Moves in the order they are entered. This may not match the actual execution order.
  Notably, it seems in the game all altitude changes are reordered to happen at the beginning of the turn on Done submit. This is not reflected in the Move list, So moves made after a number of alt changes may not have enough MP. This is true of the boardview movement sprite display also, so is a general issue.

• in Firing phase, I put a chunk of work into getting the ToHit modifiers to display and update correctly, but the penalty for Spotting still is not applied to the user displayed ToHit. It is correctly calculated when the Turn is executed though.

[SJuliez]

Few minor things.

I like the AbstractBoardOverlay and the EntityAttackLog classes. Both neat as well as the PR itself of course.