Rename `POWERLINE_THEME_CONFIG` to `POWERLINE_THEME_OVERRIDES`

Ref #1126

docs/source/configuration/local.rst

@@ -80,7 +80,7 @@ are taken from zsh variables.
     VALUE}}``. All pairs are then recursively merged into one dictionary and 
     this dictionary is recursively merged with the contents of the file.
 
-``POWERLINE_THEME_CONFIG``
+``POWERLINE_THEME_OVERRIDES``
     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/bindings/zsh/__init__.py

@@ -41,7 +41,7 @@ class Args(object):
 
 	@property
 	def theme_override(self):
-		return get_var_config('POWERLINE_THEME_CONFIG')
+		return get_var_config('POWERLINE_THEME_OVERRIDES')
 
 	@property
 	def config_path(self):

tests/test_shells/input.zsh

@@ -4,7 +4,7 @@ setopt interactivecomments
 setopt autonamedirs
 if test -z "$POWERLINE_NO_ZSH_ZPYTHON" ; then
 	function set_theme_option() {
-		POWERLINE_THEME_CONFIG[$1]=$2
+		POWERLINE_THEME_OVERRIDES[$1]=$2
 		powerline-reload-config
 	}
 	function set_theme() {
@@ -23,7 +23,7 @@ else
 	}
 fi
 source powerline/bindings/zsh/powerline.zsh
-typeset -gA POWERLINE_CONFIG_OVERRIDES POWERLINE_THEME_CONFIG
+typeset -gA POWERLINE_CONFIG_OVERRIDES POWERLINE_THEME_OVERRIDES
 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