Time scale selector should be modified

[bestchai]

The current time scale selector consists of a text field in which the user can input a value to be used as the minimum distance between two consecutive nodes on the graph, and a button to refresh the graph.

Suggestion: Implement the time scale selector as a slider, placing it under the search bar to make use of the blank space. The slider values should be calculated automatically, and range from a complete "Zoom Out" option, in which the user could see the whole log in one screen (without having to scroll), and a complete "Zoom In" option, in which the smallest time difference between two events in the log (aside from zero) would be scale to the smallest time difference in screen.

[Issue created by mhnnunes: 2016-08-11]