Add support for missing fingerprint unlock messages

[el-Basketo]

Description

Current situation:

Support for parallel unlocking with fprint was added a couple hours ago in #514

I did some testing. It works wonders! A few features are understandably still missing.

The variables

general:fingerprint_ready_message
general:fingerprint_present_message

are a nice way for the user to display and customize the feedback messages from fprintd.

Missing feature:

The two above-cited variables do not cover all fprintd states, which means that the user cannot customize all the possible values $FPRINTMESSAGE will take. We need more variables similar to general:fingerprint_ready_message to cover all possible states of fingerprint unlocking.

Hints and personal testing:

I have found at least 4 of the states not currently covered – where I assume the value of $FPRINTMESSAGE comes directly from fprint – that cannot be customized:

1. "Could not match fingerprint. Try again." Using a finger not enrolled yields it.
2. And a 2nd one very similar to the 1st, which I can't replicate, so I don't know the exact text. I will edit if I manage to get it again.
3. "Fingerprint auth disabled: too many failed attempts" After failing too many times.
4. "Unknown fingerprint error, disabling fingerprint auth" When waking up from sleep. (Yes I'll open a separate issue)

It is worth mentioning that those messages are not the same as the ones the gnome polkit or su username yield. Here is a sample of failed attempts in the case of su, polkit also gives the same ones:

$ su username
Place your finger on Synaptics Sensors
Failed to match fingerprint
Place your finger on Synaptics Sensors
Failed to match fingerprint
Place your finger on Synaptics Sensors
Failed to match fingerprint
Password:

EDITS, in order:

• formatting
• added 4th unsupported state