Add stepForward() and stepBack() functions to Scripting API

[#46375033]
Make ScriptingAPI functions public properties of ScriptingAPI object

[#46375033]

Previously they were available only in global namespace.
Now it's possible to access these functions without referring to the
global namespace, e.g.:

var scriptingAPI = new ScriptingAPI(...);
scriptingAPI.api.start()

It will be useful for interactive components, which can use this api.
Add basic version of new playback controller (interactive component)

[#46375033]

It's styled to match Upstatement design. Also now it's implemented as
independent interactive component. To control model, it uses
ScriptingAPI functions.
Bind playback controller to appropriate events, update play/pause button

[#46375033]
Do not setup model player in semantic layout

[#46375033]

It will be no longer necessary.
Place playback controller in the bottom bar

[#46375033]
Don't setup old playback component in model view

[#46375033]
Don't set padding for old playback component in model view

[#46375033]
Change slightly styling of playback controller

[#46375033]

To fit better white background.
Add time display to the play / pause button

[#46375033]
Remove depreciated, global model_player object and its method calls

[#46375033]
Add isStopped() function to Scripting API

[#46375033]
Handle keyboard shortcuts using ScriptingAPI instead of model_player

[#46375033]
Remove src/common/components as no single file from this dir is used now

[#46375033]
solar-system: add timeStepsPerTick for new playback
solar-system renderer: remove hard-coded time*0.1
spelling corrections

[#47499545]

Thanks Cynthia!
Support "controlButtons" in new playback controller

[#46375033]

"", "play", "play_reset" and "play_reset_step" values are now
supported.
more spelling corrections

[#47499545]
fix Bob's model so that export data works

IS [#47396005]