Simpler version consideration

[allenzhuaz]

Thanks to @keaven Suggestion, for the iterative graphs update, to avoid user manually input boundaries, we can consider only leaving the two options for group sequential design setting:

1. uploading gsDesign and allow user to only input observed p-value
2. uploading gsDesign and automatically calculate seq-pvalue

Pay attention to include Logic for updating graph -> update design boundary based on re-allocated alpha