Fix first paragraphs, shorten titles.

[myteron]

While looking through the title's as part of #1009 we found some issues:

• First paragraphs lead to misinterpretation and need to be corrected, such as pyscg-0040
• Contradicting content such as 0053 vs 0003 "Avoid using bit shifts for Arithmetic"
• Misplaced content such as 0043 discussing Locale as main subject but also containing a "encoding" example that needs to move to 0045
• Potentially duplicated content.

Overall this only starts to become visible after we started moving related rules into the new sections. Similar content is now much closer to each other.