Issue Summary

Provide the ability for users to configure the time to display a slide in wallboard slideshow. 

Based on the information in JRASERVER-36894: Cycle period in 'Setup Wallboard Slideshow' does not apply, the time a slide is displayed (before moving on to the next slide) is 10 seconds and this value cannot be changed.

From observation, each slide displays 2 to 3 gadgets at a time. In certain use cases, 10 seconds is not enough to review the information on the gadgets.

In "Configure wallboard slide show" menu, the configuration parameters Transition effect and Change dashboard display every only appliy to transitions between dashboards selected for the wallboard slideshow.

Furthermore, the slide interval of 10 seconds is not honoured if the Change dashboard display every time is up (See Actual Results section for example).
 

Steps to Reproduce

1. Create two dashboards
   1. Dashboard A containing 4 gadgets; G1, G2, G3 and G4
   2. Dashboard B containing 2 gadgets; G5 and G6
2. Set the "Change dashboard display every" setting to 15 seconds
3. Click on "View wallboard slideshow"

Expected Results

• The time interval between slides can be configured
• If the time interval between slides overlaps with the time interval between dashboards (i.e. the value set in "Change dashboard display every" setting), honour the slide time interval before transitioning to the next dashboard.

Actual Results

Workaround

Treat each dashboard in the wallboard as a slide, so that "Change dashboard display every" setting can be used as the time interval between slides.