set suitable defaults for new features

[bh9]

When features are added, the metalnx.properties file changes. When changing version, there should be defaults in place such that the file doesn't need to change unless one wants to enable one of the new features. This is not the case with pluggable search, as the startup errors out with

2021-03-25 16:44:47 WARN  XmlWebApplicationContext:551 - Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException:
...
nested exception is java.lang.IllegalArgumentException: Invalid boolean value [${pluggablesearch.enabled}]

Checking for unset values and assuming them to be false would mean that these wouldn't actually have to be set, so upgrades could be done without first changing the properties file

[trel]

Completely agree.

We should have a strong default for every setting, and log messages saying that default value was being used, for admin discoverability along the way.

[trel]

out of time - bumping.