dts: update docstrings

Format according to the Google format and PEP257, with slight
deviations.

Signed-off-by: Juraj Linkeš <[email protected]>

Author: jlinkes

dts/framework/__init__.py

@@ -1,3 +1,13 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright(c) 2022 PANTHEON.tech s.r.o.
 # Copyright(c) 2022 University of New Hampshire
+
+"""Libraries and utilities for running DPDK Test Suite (DTS).
+
+The various modules in the DTS framework offer:
+
+* Connections to nodes, both interactive and non-interactive,
+* A straightforward way to add support for different operating systems of remote nodes,
+* Test suite setup, execution and teardown, along with test case setup, execution and teardown,
+* Pre-test suite setup and post-test suite teardown.
+"""