Use adaptive Buffer algorithm

[kleinweby]

The aim is to make the User Interface as responsive as possible.

Therfore when we know the progress will be shown we should use a algorithm which updates often without inflecting on the performance when using to many updates.

An idea would be:

• use a maximum of n bytes
• measure the duration for the buffer to fill, adjust the buffer so that a buffer file takes between 150-250ms
• use at most 1/10 of the available lines as buffer

Always align the buffer to line boundaries.