Create the ability to call up an npc dialog within an event
Initial version of NPC Action menu.
Make use of the new NPC action menu.

Potential implementation for issue #367
Made the actionlabels to be center justified and fixed hilight
of current item.
Remove the vendor button from MenuTalker.
Made some labels more descriptive
Add support for dialog grouping to provid random rolled dialogs
from a group.

Potential solution for issue #371
Place the NPC Action menu above player instead of a
hardcoded y offset from top.
Make NPC_VOX_INTRO sound play when entering shop.
Load creature sounds when transforming

Closes #354
Moved some variable to GameStatePlay instead of MapRenderer
Show the NPC Action menu again when an dialog is ended for viewing
possible new dialogs topics.
Added initial theaming for text colors in action menu.
Do not start autoselected action automatic after ending a dialog.
Added check for empty() menu and depend on it if we should show
NPC action menu or not.
Introduce AvatarStatBlock class.
Convert the user interfacing classes to use the AvatarBlockStats class.
calculate derived stats on the fly instead of caching those.
Move hero_cooldown to AvatarStatBlock.
Entity has a StatBlock pointer now.

needed to fit in the subclasses.