Refactor the Feature framework

Refactor the Feature framework

run() returns the expected status code (see following JIRA tickets).
repo, pre() and post() are removed as they were quite useless.
A dedicated class is proposed for bash programs.
Unit tests have been added to fully cover this module.

All features have been modified to conform with these modifications.
It also removes the decorators which skipped several unit tests.

JIRA: FUNCTEST-778
JIRA: FUNCTEST-779
JIRA: FUNCTEST-780
JIRA: FUNCTEST-781

Change-Id: Ifb1e4c4f68260a4e20d895f67f07f369ca959374
Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>