lua-guidelines: Add rule about empty lines around begin-end things
development-guidelines: Add rules about format of TODO
development-guidelines: Add rule about comments depersonalization
lua-guidelines: Fix personalized comments
development-guidelines: Delete missing rule 6

Also make the list less affected by possible future changes.
lua-guidelines: Delete trailing whitespace
lua-guidelines: Delete FIXME#1

Looks outdated, there seems to be enough examples.
lua-guidelines: Fix FIXME#2, add examples

Also fix wrong concatenation indent
lua-guidelines: Fix FIXME#3, add examples
lua-guidelines: Fix indent after "return"