485 create dataset url

[ChengShi-1]

What this PR does / why we need it:

We decided to modify the URL path for the 'create dataset' page to maintain consistency with the 'create collection' structure.

The changes are as follows:
Old path: /spa/datasets/create?collectionId=[collectionId]
New path: /spa/datasets/[collectionId]/create

Which issue(s) this PR closes:

• Closes Create Dataset URL #485

Special notes for your reviewer:

Originally, we have /spa/datasets/create could be accessible, but after updating, it wouldn't work.

Suggestions on how to test this:

1. Click the header "Add Data" => "New Dataset", check if the url is correct
2. On the main page, click the button"+ Add Data" => "New Dataset", check if the url is correct

Does this PR introduce a user interface change? If mockups are available, please link/include them here:

No

Is there a release notes update needed for this change?:

No

Additional documentation:

The Developer_Guide doc changes, because this change relates to a testing example shown on the developer guide.

[coveralls]

coverage: 97.397% (+0.001%) from 97.396%
when pulling c9a36cd on 485-create-dataset-url
into 4dc5ff1 on develop.

[g-saracca]

Everything looks more than good! Approving

[ekraffmiller]

looks good! merging