Support ACL's when connecting to Redis store.

We only have the means to generate a transient NameID. If a different
one was requested, the code would crash because nameIdValue would
be unset. Fix that we fall back to transient in such a case.

No functional changes

Remove inappropriate output encoding

Output encoding happens in the view. This prevents the encoded stuff
from ending up in other places, including log files. Also fixes
tests that were broken because of this.

Document store.redis.password in config.php template.

Support for this option was previously added in
https://github.com/simplesamlphp/simplesamlphp/pull/1012

Date needs to be removed since this is implicit in syslog. For safety,
remove it only when at the start of the string (default format).
If someone creates a custom string they can leave out date entirely
if it's not at the start of the string.

Being more specific fixes that before elements of the actual log
message were eaten by this regexp if they contained a '%'.

Closes: #1549

Partially reverts b7c2caad
and fc1ffee7

Closes: #1660

This reverts commit 8bd8e3f4.

This reverts commit cd4cb9d4.

Closes:  #1659

Remove automatic entityID-generation

Fix NameID generation