dnssec-settime: Allow manipulating state files

dnssec-settime: Allow manipulating state files

Introduce a new option '-s' for dnssec-settime that when manipulating
timing metadata, it also updates the key state file.

For testing purposes, add options to dnssec-settime to set key
states and when they last changed.

The dst code adds ways to write and read the new key states and
timing metadata. It updates the parsing code for private key files
to not parse the newly introduced metadata (these are for state
files only).

Introduce key goal (the state the key wants to be in).