Add ability to filter only failed / errored tests in list of executed tests #73

The ability to sort results by status in the grid is great.
It wold be even better if the plugin would allow to narrow down the list of visible test to:

• only failed & errored
• only failed & errored & warnings
• only failed
• only errored
• only warnings

This could be implemented as toggles:

• show/hide success
• show/hide warnings
• show/hide errors
• show/hide failures

The functionality would be very useful when using "tree" view to display test results.