Magic improvements

[thokkat]

Some refactor/cleanup of the switch statements e.g. fallback for teleport spells is no longer needed after changes to animation start function.

PR has fixes for these issues:

• SPL_DONTINVEST allows the player to hold the charged spell until key is released. investedMana is then no longer accumulated.

Gothic 1 exclusive:

• A lot of spells ( i.e teleport, firerain) use the SHOOT animation as cast animation. If castLevel is in CS_Cast range SHOOT animation would be started a second time after spell is already sent. To prevent this play animation only if CAST animation exists.
• When a teleport spell is aborted transition to idle animation could be skipped by walking forward. CS_Finalize is now handled like CS_Emit except spell is not committed.
• For code=SPL_NEXTLEVEL change castLevel only if castLvl<15 instead of castLvl<=15. Otherwise it was possible to jump from CS_Invest to CS_Cast which broke spells like summon demon with a long cast phase.

[Try]

Look good - merged.
Thanks @thokkat !