BETA: Continuing with [6249] rework:

	* Adding method overload (just wrappers) to `L2Skill`.applyEffects(..) to avoid useless parameters.
		* Suggested by: jurchiks
	* Added a new parameter to `L2Skill`.applyEffects(..) to customize skill abnormal time upon casting.
	* Changed the way we check if we can apply a buff (debuff, etc) to a character.
		* Now all checks must be done on `AbstractEffect`#canStart(`BuffInfo`), this way we prevent executing `AbstractEffect`#onStart(`BuffInfo`) logic if the effect won't be added to the effect list.
			* `AbstractEffect`#onStart(`BuffInfo`) is void now.
		* Now `AbstractEffect`#onStart(`BuffInfo`) is called when the effect is already placed in the effect list, the old effect has been removed and we are sure the new effect should be activated.
		* Reported by: nBd
		* Suggested by: nBd
	* Reworked the way effects are restored into characters (players, summons).
		* Avoiding the restoration of instant effects.
			* Reported by: nBd, UnAfraid, Nos
		* Reusing `L2Skill`.applyEffects(..) code!
	* Fixed effects flags not being computed for players (sleep, hide, etc not removed).
		* Reported by: nBd, thorl2
		* Suggested by: nBd
	* Fixed many system messages:
		* "$c1 has resisted your $s2" is not displayed when adding active skills or switching subclasses.
			* Reported by: nBd, UnAfraid, Adry_85
		* "$s1 has worn off" is not displayed for passive skills when they are removed.
	* Fixing summons not getting buffed when master receives  buffs.
		* Reported by: nBd
	* Fixed summons not getting Celestial Shield.
		* Reported by: Zeldak

'''Note to developers:''' Instant effects should not override `AbstractEffect`#canStart(`BuffInfo`), all checks should be done `AbstractEffect`#onStart(`BuffInfo`).