Support multiple methods in compound/macro tasks.

[tbillington]

As mentioned on discord, just noting here that "Methods" in "Compound Tasks" as mentioned on page 5 in this description of HTNs are missing from the implementation :) https://www.gameaipro.com/GameAIPro/GameAIPro_Chapter12_Exploring_HTN_Planners_through_Example.pdf

[QueenOfSquiggles]

Adding a note that it was after this issue was posted that I added issue templates. No need to change it as it works just fine. (Trying to pre-empt any white-knighting)