Support for Double Charts (双打譜面)

[sakurada0291]

Double charts refers to a type of charts that has a different layout of patterns differentiating it from 1P's Side.

Examples are the following:

Koi
https://www.youtube.com/watch?v=YJoCeZEIMhw

KAGEKIYO
https://www.youtube.com/watch?v=BExqqDyAFG8

Soul Calibur II
https://www.youtube.com/watch?v=eAmxdl6CzO4

WE WILL ROCK YOU
https://www.youtube.com/watch?v=nEt-ZZkJxMU

Bug report
If a chart is 双打 (or double chart), it shows out a bug that it doubles a character from the start of the letter, for example, (ソウルキャリバーII) becomes (ソソウルキャリバーII), no file or directory exist. (bug) when importing (i use 0.5p8)

Improvement
On the other hand, if there is a TJA command such as STYLE:Double, #START P1 and START:P2, set "doublePlay" to true.
for single player only and if has the command STYLE:Single, set "doublePlay" to true also. this applies to music_attribute.