fix ele t10

[lime-green]

Closes #3918

Instead of extending 6s statically, it should round to the closest tick:

https://totemz.wordpress.com/tag/elemental-shaman-tier-10/
https://web.archive.org/web/20100808192139/http://elitistjerks.com/f79/t76510-elemental_patch_3_3_now_more_fire_nova/p25/

From EJ, hasn't been tested on live yet but it should work like this, the static 6s was how it used to work before 3.3:

20% haste (656 haste = 2.5s ticks)
SINGLE: 1 refresh, 8 ticks each time (6 + 2)
MAX: 3 refreshes, 12 ticks both times (6 + 3*2)
Time for #ticks:
*2 = 5
*3 = 7.5
*4 = 10

29.58% haste (970 = 2.32s ticks)
SINGLE: 1 refresh, 9 ticks each time (6 + 3)
MAX: 5 refreshes, 21 ticks both times (6 + 3*5)
Time for #ticks:
*2 = 4.64
*3 = 6.96
*4 = 9.28


50% haste (1406 haste +WoA = 1.9997s ticks)
SINGLE: 1 refresh, 9 ticks each time (6 + 3)
MAX: 3 refreshes, 15 ticks both times (6 + 3*3)
Time for #ticks:
*2 = 3.9994
*3 = 5.9991
*4 = 7.9988

74.18% haste (1458 haste +WoA +EM = 1.719s ticks)
SINGLE: 1 refresh, 9 ticks each time (6 + 3)
MAX: 3 refreshes, 15 ticks both times (6 + 3*3)
*2 = 3.438
*3 = 5.175
*4 = 6.876

75% haste (1474 haste +WoA +EM = 1.7140s ticks)
SINGLE: 1 refresh, 10 ticks each time (6 + 4*1)
MAX: 4 refreshes, 22 ticks both times (6 + 4*4)
Time for #ticks:
*2 = 3.428
*3 = 5.142
*4 = 6.856

100% haste (899 haste +WoA +EM +BL = 1.4999s ticks)
MAX: 3 refreshes, 18 ticks (6 + 3*4)
Time for #ticks:
*2 = 2.999
*3 = 4.499
*4 = 5.999

149.2% haste (1928 haste +WoA +EM +BL = 1.2035s ticks)
MAX: 2 refreshes, 16 ticks both times (6 + 5*2)
Time for #ticks:
*4= 4.813
*5= 6.017
*6= 7.220