[PATCH 12/17] binman: Update the section documentation

[Simon Glass]

Expand this to explain subclassing better and also to tidy up formatting
for rST.

Fix a few pylint warnings to avoid dropping the score.

Signed-off-by: Simon Glass <sjg at chromium.org>
---

 tools/binman/entries.rst      | 149 +++++++++++++++++++++++++++-------
 tools/binman/etype/section.py | 148 +++++++++++++++++++++++++++------
 2 files changed, 242 insertions(+), 55 deletions(-)

Applied to u-boot-dm/next, thanks!