BCS 746-000808

Fix pylint errors introduced with new pylint version:
* unspecified-encoding: explicitly set encoding when opening a file
* assigning-non-slot: use "set_reference()" function instead of assigning
  a value to the "reference" attribute
* unused-variable: remove "e" variable on exceptions when not referenced

Previously the default branch was allways used to generate the tests
from, now it is possible to specify the branch as cmdline option.
Additionally, the revision of the test repository is added to the
call of the test generator, so the tests run at a fix rev.

BCS 746-000547

Uses submit_all instead of submit.
Some code cleanup also.

The testsuite is generated per platform and submited to the lava server.
The resulting jobs are monitored and the results are downloaded in the
results/ subfolder.