Ver. 1.2.1: Save slot character images

This is a generally recommended update.

Added Features:

• Character rules can optionally apply to the party shown on save slots (applied when saving; mind the note of caution!).
• Image loading errors can be ignored when viewing the save slot list.

Fixes:

• Fixed tags not persisting across save/load. This changes the plugin-specific save data, but the new version is backwards-compatible with earlier saves.

Revisions:

• Added compatibility note regarding RPG Maker Animation Solution.
  Our plugins were compatible beforehand already, since we target different parts of the Character graphics system, but now it’s documented.

• The source-code is now largely typechecked.
  I fixed a number of mistakes while implementing that, though they seem to have been obscure enough that I didn’t receive any complaints.
  (This was mostly related to directly Event-controlled character tags.)

NOTE: Save files created with this version of the plugin may not be compatible with older versions of it!