Make SoundManager support playing sound on locations, were distance
from location to pc controls the amplitude, eg. the further away the
sound is the more faint it is played out.

Made Map events on_load special for looping a sound effect at the
position of the event, this will be used for location based env.
effects like the fires we now have in warp zone and atrium.
Merge pull request #387 from stefanbeller/master

Calculate derived stats on the fly instead of caching those.
Rename sfx to soundfx for consistency in data files.

Fixes #388
Merge pull request #389 from hean01/env_sound

Support for location based environmental sound effects.
Merge pull request #390 from hean01/soundfx_attribute

Rename sfx to soundfx for consistency in data files.
Fix linear, topic-less dialogs
Merge pull request #392 from dorkster/npc

Fix linear, topic-less dialogs
Remove section "Running flare" from README.engine
Install instructions: add fedora dependencies.
installation instructions: Remove python and standard gcc for openSUSE

There is still gcc-c++ which is enough.