Improve the UI based on curators' suggestion

[jiyue1214]

Improve the UI design based on curators' feedback to https://ebispot.github.io/gwas-sumstat-format-was/

[jiyue1214]

Feedbacks:

• [x] Show if the file is selected successfully
• [x] Instructions/documentation on how to edit the configure file
• [ ] Step 3 is too long to read
• [ ] User may easily miss the step 5
• [x] text box about the configure file part is not friendly to read
• [ ] Explain what the test button means, and the difference from the apply button
• [x] activate the validation button if someone only wants to run the validation step.
• [x] Delete the md5 which is not useful in the configure file
• [x] Hight to distinguish the example and input table ~~- [ ] stop suggesting renaming not mandatory columns~~ (we can suggest the users are always free to change them back)
• [x] If the rename is empty, keep the original field name
• [x] collapse the tables
• [ ] suffix in the configure file and sane file name in the UI is confusing ~~- [ ] Merge the grant permission and select files into one button~~ (cannot do it since the file system requirement)