Make hull stealth and detection descriptions agree with game mechanics.

[LGM-Doyle]

The adjective used to describe ship hull stealth and detection were not
consistent with the numbers for game mechanics or other descriptions.

The adjectives used were: very low, low, poor, average, moderate,
normal, high, good, and excellent.

I reduced the used adjectives to: very low, low, medium, high and very
high.

The tables show values for each value of stealth or detection the number
of hulls, the adjective and the type of empire scanner capable of
detecting that level of stealth:

Stealth Value: -55 -35 |-15 -5 | (0) 5 | 15 25 | 35 45
Number: 1 1 | 1 2 | 0 17 | 2 3 | 4 2
Adjective: v.low | low | medium | high | v.high
Scanner: Basic (10) | Active(30) | Neutron (50)

Detection Value: 10 | 25 | 50 | 75 100
Number: 1 | 25 | 4 | 2 1
Adjective: low | medium | high | v.high

I chose medium to be the most typical stealth or detection value.
I chose high and very high stealth to correspond to the thresholds for
the active and neutron scanners.
Note, negative stealth is not displayed in game, but it affects results.

[geoffthemedio]

'''A hull designed to create a colony on a planet in the same system in which it is produced. The hull is unable to move between systems.

[[encyclopedia STEALTH_TITLE]] is medium and [[encyclopedia DETECTION_RANGE_TITLE]] is medium.

[LGM-Doyle]

This PR was originally only intended to fix the consistency of the detection and stealth descriptions.

I will make these changes, but not today.

[geoffthemedio]

haven't carefully checked the actual changes, but I assume they are reasonable...

[Ouaz]

• I bring the changes into the FR stringtables, and I noticed that some "average" adjectives are still there (line 10562; 10572; 10582; 10592; 10602; 10612; 10622; and 10900), although you removed it from the new reduced list of adjectives (very poor, poor, medium, high, very high). Is this intended?
• There's also a "good" adjective on line 10723 (SH_ORGANIC_DESC)
• A "moderate" on line 10871 (SH_FRACTAL_ENERGY_DESC) and 10881 (SH_QUANTUM_ENERGY_DESC)

Good work though, a lot more convenient and consistent.

[LGM-Doyle]

@Ouaz I only checked stealth and detection for consistency, so I only changed the adjectives for stealth and detection.