Refactoring louloulibs and cmake

Use OBJECT libraries
Remove the louloulibs directory
Write FOUND variables in the cache

cmake: Improve the usage of PARENT_SCOPE

Remove the embedded sha1 code, and use one of botan or gcrypt

This adds a hard dependency on one of Botan or gcrypt. Botan is already a
recommended dependency, and gcrypt is probably packaged almost everywhere,
so this should not be a big deal.

ref #3241