Adjust collaborators section style

[jkicillof]

• [x] Checks for active collaborators should be black, not blue
• [x] The table should have a minimum of 5 rows even if they are less collaborators
• [x] Show remove icon only on row hover

https://projects.invisionapp.com/d/main#/console/12115078/299944180/preview The data table style adjustments are on issue #179

[mmuller]

Working properly in version 23e93ec Remove icon is always displayed, the tooltip with the message Remove collaborator is displayed on row hover.