Allow immediate extra addition/removal in ruleset

[danau]

Similar to http://forum.freeciv.org/f/viewtopic.ph ... a77dd9a2fb, but for adding and removing of extras.
For my own ruleset I'm specifically interested in "free pillaging" that allows units to destroy certain improvements and move on in the same turn (pillaging with 0 movement costs).
I can imagine that this might also be useful for "quick road building" type of rulesets, where a single unit could build road on multiple tiles in the same turn.

[Elefant]

Lua should allow this in conjunction with the actor tile fake generalized action.