Add test for health effect on healing rate

[wapcaplet]

Summary

SUMMARY: Infrastructure "Add test for health effect on healing rate"

Purpose of change

To expand the unit tests of Character::healing_rate to include the effect of the "hidden" health stat.

Describe the solution

Adds a new test case with examples covering:

• Normal health (0) gives normal healing rate when asleep
• Bad health degrades healing when asleep (down to NO healing at -200 health)
• Good health improves healing when asleep (up to 2x healing at +200 health)
• Health has no effect on healing while awake

Also uses a couple new consts for the quality of rest factor (0 awake, 1 asleep) to make the tests a little more self-documenting.

Describe alternatives you've considered

An enigma wrapped in a burrito and smothered in "que? so?"

Testing

tests/cata_test [heal][health]

[wapcaplet]

Travis CI Android build says it's failing, but I don't see any errors, only this warning:

/home/travis/build/CleverRaven/Cataclysm-DDA/android/app/jni/src/lightmap.cpp:1247:32: warning: unknown warning group '-Wimplicit-int-float-conversion', ignored [-Wunknown-warning-option]
#pragma GCC diagnostic ignored "-Wimplicit-int-float-conversion"
                               ^
1 warning generated.

The XCode build is failing on unrelated effective DPS tests.