Merge pull request #528 from chrox/master

code refactoring
cleanup: expand tab to 4 spaces
Merge pull request #531 from chrox/retab

cleanup: expand tab to 4 spaces
The last code changes resulted in crashes. Now they don't and it the fine tuning is improved.

It changes `steps` in line 13 for better finetuning,
`rate` in line 22 so that it has a nil value for `Kobo_phoenix'
and delta_int in line 48 to the last know working syntax.

Could someone check whether line 22 does result in 3.0 for non-phoenix devices?
switch license to AGPLv3