log viewport to limit size of text displayed for performance

[dufoli]

• in log.js create a system in render to only display the text display on screen (same system than done on data-load for dataTable)
• vertical autoscroll on search

[Dufgui]

The goal here is to not apply parseLog on one lines but on a small part according to scroll.
To do it we can take as example data-load.js

[dufoli]

@Dufgui not sur if it is really usful for this version. I postpone it.