DBFunctions: Fix Event creation

refs #4901

With passing parameters directly to the DB, do not use string 'NULL'
instead of None/NULL.  Remove this fallback from insertIntoEvents, as
getAgentForFileUUID return None by default. Actual agent values do not need
to be double quoted, so just return the value instead of the string with
quotes around it.
Revert "updating mysql files"

This commit fixed the mysql files as used in packages,
but broke dev-helper based installs.

Reverting so change can be included in dev/issue-7072-upgrade branch

This reverts commit 327f735528d2eb4d6c72dfe45c041fe8bddcc7e0.
createMETSRights: namespace PREMIS elements

Fixes #7210.
createMETSDspace: fix mdRef prefix

Fixes #7212.
createMETSTrim: namespace elements