DateRangePicker disable the confirm button when user did not complete the selection of start datetime and end datetime

[kurobanekid]

This function solves the problem (这个功能解决的问题)

Avoid that the user has selected the start datetime, but has not selected the end datetime, and then go to confirm. The result at this time is not what the unfamiliar users wants.

Expected API (期望的 API)

1. Add a new attribute called complete-disabled. (The name may also need to be considered.)
2. When user selecting the end datetime, don't instantly update the model value. The model value will not update until the user select the end datetime.