Ticket27135 store obs bw

also:
* fix missing avg bw after moving functions to methods
* add more attrs to V3BWLine that are going to be used by other
  scaling methods

instead of conf and args, so that it's easier to test the method
without creating ConfigParser and ArgumentParser objects.

1. magic methods
2. classmethods
3. staticmethods
4. properties
5. methods

1. magic methods
2. classmethods
3. staticmethods
4. properties
5. methods

1. magic methods
2. classmethods
3. staticmethods
4. properties
5. methods

Ticket27512 warn disk followup

It will only be shown when running sbws without arguments.

since some systems might not allow it.

since some systems might not allow it.

trac: finishes #26937

getpath is necessary so that ~ is expanded

GH: closes #241
trac: implements #26937

getpath is necessary so that ~ is expanded

GH: closes #241
trac: implements #26937

This reverts commit ede9feda3b6285c9e04a162dc393afa5e734d7e3.
An exception trying to write to log file when there is not disk
space can happen anywhere in the code

This reverts commit 72b45d4d5b5ccd7228ab793012ba7d42084ddfbf.