Implement a few gui tweaks to the details panel so that it looks better on small width terminals

[Paliak]

• Sets MAX_HISTORY to 64 so that it is a power of 2
• Tweaks graph width calculation to prevent it from wrapping (56x30 terminal size for the below screens):
  Before:

After:

• Removes redundant information from the details panel to clean it up a bit
• Hides the Error line in the left panel unless there actually is an error
• Makes the whole graph render even when there aren't enough samples to cover the whole width

[laixintao]

awesome fix, thanks