Rename `POWERLINE_CONFIG` to `POWERLINE_CONFIG_OVERRIDES`

Fixes #1124
Ref #1126

docs/source/configuration/local.rst

@@ -73,7 +73,7 @@ Zsh/zpython overrides
 Here overrides are controlled by similarly to the powerline script, but values 
 are taken from zsh variables.
 
-``POWERLINE_CONFIG``
+``POWERLINE_CONFIG_OVERRIDES``
     Overrides options from :file:`powerline/config.json`. Should be a zsh 
     associative array with keys equal to ``KEY.NESTED_KEY`` and values being 
     JSON strings. Pair ``KEY.KEY1 VALUE`` is equivalent to ``{"KEY": {"KEY1": 
@@ -83,9 +83,10 @@ are taken from zsh variables.
 ``POWERLINE_THEME_CONFIG``
     Overrides options from :file:`powerline/themes/shell/*.json`. Should be 
     a zsh associative array with keys equal to ``THEME_NAME.KEY.NESTED_KEY`` and 
-    values being JSON strings. Is processed like the above ``POWERLINE_CONFIG``, 
-    but only subdictionaries for ``THEME_NAME`` key are merged with theme 
-    configuration when theme with given name is requested.
+    values being JSON strings. Is processed like the above 
+    ``POWERLINE_CONFIG_OVERRIDES``, but only subdictionaries for ``THEME_NAME`` 
+    key are merged with theme configuration when theme with given name is 
+    requested.
 
 ``POWERLINE_CONFIG_PATHS``
     Sets directories where configuration should be read from. If present, no 

powerline/bindings/zsh/__init__.py

@@ -37,7 +37,7 @@ class Args(object):
 
 	@property
 	def config(self):
-		return get_var_config('POWERLINE_CONFIG')
+		return get_var_config('POWERLINE_CONFIG_OVERRIDES')
 
 	@property
 	def theme_option(self):

tests/test_shells/input.zsh

@@ -8,8 +8,8 @@ if test -z "$POWERLINE_NO_ZSH_ZPYTHON" ; then
 		powerline-reload-config
 	}
 	function set_theme() {
-		typeset -A POWERLINE_CONFIG
-		POWERLINE_CONFIG=(
+		typeset -A POWERLINE_CONFIG_OVERRIDES
+		POWERLINE_CONFIG_OVERRIDES=(
 			ext.shell.theme $1
 		)
 		powerline-reload-config
@@ -23,7 +23,7 @@ else
 	}
 fi
 source powerline/bindings/zsh/powerline.zsh
-typeset -gA POWERLINE_CONFIG POWERLINE_THEME_CONFIG
+typeset -gA POWERLINE_CONFIG_OVERRIDES POWERLINE_THEME_CONFIG
 set_theme_option default_leftonly.segment_data.hostname.args.only_if_ssh false
 set_theme_option default.segment_data.hostname.args.only_if_ssh false
 set_theme default_leftonly