allow configuring scram arch for everything, fixes #3257

Allows to setup a default scram arch for all releases and then
overrides for specific releases. This reduces the amount of
configuration options as one specific release is only used
from a single scram arch no matter in how many places in the
Tier0 it is configured.

Express and Repack CMSSW overrides are now not stored as
overrides anymore but stored in the repack_config or
express_config database tables. Also store the optional
extra second step reco release for Express and store
scram arch for all choices separately. The reco_config
table keeps its CMSSW version and scram arch columns.

The stream cmssw association table now only has the
online CMSSW version, the override was removed as it
isn't needed anymore.

Also get rid of all PromptSkim releated code.
Merge pull request #4059 from hufnagel/scramarch

allow configuring scram arch for everything, fixes #3257