Showing a busy indicator when log is being processed

Processing a long log takes time. It's important to signal to the user that the tool is actively working, and is not stuck. The simplest solution is to (1) place an overlay over the input screen so that it is seen as disabled, and (2) use a busy indicator that animates a simple shape until the log is processed. Here is an example of a gif we can use:

[Issue created by bestchai: 2016-08-05]