Throw the exception in the `LyricTimeTagsChangeHandler.Shifting()` if shift the first time-tag to the left.

[andy840119]

Not very sure should it be a good method because it can be simply to:

TimeTag Shifting(TimeTag timeTag, TimeTagIndex index);

[andy840119]

Inspired from the #1973
Not very sure should remove this method because dragging time-tag might not be a needed feature?