Fix max hp being calculated too early, added boss hp scaling for frostallion, and reflect iv changes on in-game stats immediately

[KrisCris]

Issue:

• Frostallion is missing the boss hp scaling.
• maxhp calculated too early, and the stats panel is not displaying the true data
• 

Fix:

• Frostallion is missing the boss hp scaling.
• MaxHP is calculated ahead of pal's rank/level/iv update
• Health Stat UI is not using the true save data

Feat:

• display updated stats immediately after changes saved

[KrisCris]

Apologize if any confusion was caused by my old handleMaxHealthUpdates(self, pal, changes) method - the changes arg is the key for ensuring the correctness of the HP calculation even if in the wrong order, for the old methods introduced in PR: https://github.com/magicbear/PalEdit/pull/1. At the time, I was trying to calculate the possible hp scaling before updating the stats, such that an alert can pop up if the difference is too big between scaling in our data and the calculated one, since some boss scalings might be missing.

after testing against all the bosses I could get in the game, I think Frostallion is the only one missing : )

and I think these can be closed:

• https://github.com/EternalWraith/PalEdit/issues/40
• https://github.com/EternalWraith/PalEdit/issues/83

[KrisCris]

Since you've done the exact same fix by yourself, and have no plan merging this PR, I am going to close it.