Rationale: no need to use upper case keywords in a .sql file. Also, this
is more coherent with the other SQL files in SWH.

update README and crontab to match

now only the variable GHLISTER_ROOT at the beginning of the crontab needs to be
properly customized

setting it properly is the responsibility of the caller

they forced configuration duplication, and were redundant anyhow

also: prefer lexer-time string concatenations to runtime ones

since quite a while cache dir is set via the conffile only

increase MAX_SLEEP a bit, as it is now used for both connection-level and
throttle-level retries

thanks copiesofcopies!