Add auto_tagk and auto_tagv fields to the Config class along with defaults
(to true for both) in preparation for #331.
Create Config.loadStaticVariables() to load the static variables whenever a
config value changes. Now overrideConfig() will reload the statics.
Change setAutoMetric() so that it will update the hash map with the given value
in case users access the config from the GUI and have toggled the flag via CLI.

Signed-off-by: Chris Larsen <clarsen@euphoriaaudio.com>
Modify Tags.resolveAllInternal() to use the new config flags to allow or block
UID assignment for tagks and tagvs. This fixes #331.
Also add unit tests for the UID creation.

Signed-off-by: Chris Larsen <clarsen@euphoriaaudio.com>