quickPsiTraining option

-Any soldier can be placed into or removed from psy-training at any time.
-Initially soldiers will start with a negative psy-skill value which will be used to determine how many more days of psy-training they need to unlock their psy-potential.
-Psy-Training calculated every day at 0:00
-Soldiers with psy-skill < 0 would get ++psy-skill each day
-Soldiers with psy-skill == 0 would get +14 to +26 psy-skill
-Soldiers with psy-skill > 0 have a chance of getting a psy-skill equal to 10/(psy-skill)
-You can anytime switch to (or from) vanilla behavior
interface improvement; return back some code.
initial training from 30 to 50 days - close to vanilla behavior
rename option to "anytimePsiTraining"; code optimisation
check psiSkill <= 0
"Improvement" column - only for training in psi-lab
PsiTraining button moved to SoldiersState.
Merge branch 'master' of https://github.com/SupSuper/OpenXcom.git into psionic_training
Advanced options description
Russian adv.option description
"_improvement" behavior changed
possibility return back vanilla behavior improved
Merge branch 'master' of https://github.com/SupSuper/OpenXcom.git into psionic_training
Avoid conflicts:
	bin/data/Language/French.lng
	bin/data/Language/German.lng
	bin/data/Language/Spanish.lng
avoid conflicts:
	bin/data/Language/Italian.lng
avoid conflict:	src/Basescape/SoldiersState.cpp
code moved to trainPsi1Day()
uses constants from ruleset
chance getting +1 psiSkill reduced
avoid conflict:	src/Savegame/Soldier.cpp
save/load _improvement