Fix a few UI glitches

[lorenzo-cavazzi]

This PR contains a few fixes. I split them in different commits so that it's easier to review the code changes separately:

1. The star button displayed an endless spinning wheel for anonymous users. Not it shows the start and it restores the behavior on click (will redirect to the login to continue)
   
2. Adjust the margins on search containers by reducing margin in equal parts on both left and right sides, instead of left only (in the screenshot, the left screen shows balanced margins, while on the right screen there is a smaller space on the left and a bigger one on the right).
   
3. Prevents invoking multiple times the projects API with the same parameters when reaching the projects page. This was worse in the case of anonymous users since they were also redirected, adding an extra query for their own projects that always returns empty since they can't have any own projects (in the screenshot, there are 3 queries on the right side, while only 1 on the left).
   
4. The projects page redirected anonymous users to the public projects page using history.push, therefore preventing any backward navigation.

/deploy renku-gateway=master #persist
fix #2014

[RenkuBot]

You can access the deployment of this PR at https://renku-ci-ui-2017.dev.renku.ch

[andre-code]

The code looks good and works as expected!
Thanks for the corrections :)

[RenkuBot]

Tearing down the temporary RenkuLab deplyoment for this PR.