Feat/565 add metric tooltip

[spacehamster87]

Content

• Adds optional, configurable tooltip field to cluster.json configurations
• Reworks "Availability" render in MetricSelection Modal
• Fix invisible navbar bug die to stuck animation on certain browser settings
• Make subcluster Filter List scrollable if amount of SCs is high

Notes

• Requires cc-lib update, see PR add tooltip field to metricconfig struct cc-lib#78
• Tooltips are not combined currently, if two identical metric-names use different tooltip-texts
• ... instead current handling is "first come, first serve"; i.e. metrics only have to have tooltips added once across all clusters.

Issue

Closes #565