Let run a scan on existing project with less permissions

[gbonnefille]

Is your feature request related to a problem? Please describe.

Currently, the permissions required to run an analysis are quite huge (Gate Admin, Project creation).
It could be useful to let a non privileged user to run an analysis on an existing project, just based on scan permission on this project.

Describe the solution you'd like

This seems mostly an UI change. The matter is that to do so we have to know the project before evaluating the permissions.

One idea: adapt the parts of current UI dynamically:

• disable Analysis button until permissions are OK
• disable Gate selection if no gateadmin permission
• update all parts when the user types the project's key.

Describe alternatives you've considered

Other option: use two distinct pages, one for new project, one for existing project...