Added env var checking to all config get methods.
Added env var checking to all config get methods.

The new method replaces the manual env var parsing with simply setting
the config's value to the env var value. This lets the normal parsing
methods do the work later, to avoid duplication of effort.

cbenhagen/buildozer,techtonik/buildozer,inclement/buildozer,rnixx/buildozer,techtonik/buildozer,bob-the-hamster/buildozer,kivy/buildozer,inclement/buildozer,superalex/buildozer,kived/buildozer,kivy/buildozer,kivy/buildozer,inclement/buildozer,kived/buildozer,kivy/buildozer,dvenkatsagar/buildozer,rnixx/buildozer,inclement/buildozer,rnixx/buildozer,rnixx/buildozer