Configurify the mappings for editing/applying the spf13 config

A user can set the following variables in their .vimrc.before.local file
to customise the key mappings:

g:spf13_edit_config_mapping
g:spf13_apply_config_mapping

the defaults are <leader>ev and <leader>sv respectively

.vimrc

@@ -285,6 +285,22 @@
         let maplocalleader=g:spf13_localleader
     endif
 
+    " The default mappings for editing and applying the spf13 configuration
+    " are <leader>ev and <leader>sv respectively. Change them to your preference
+    " by adding the following to your .vimrc.before.local file:
+    "   let g:spf13_edit_config_mapping='<leader>ec'
+    "   let g:spf13_apply_config_mapping='<leader>sc'
+    if !exists('g:spf13_edit_config_mapping')
+        let s:spf13_edit_config_mapping = '<leader>ev'
+    else
+        let s:spf13_edit_config_mapping = g:spf13_edit_config_mapping
+    endif
+    if !exists('g:spf13_apply_config_mapping')
+        let s:spf13_apply_config_mapping = '<leader>sv'
+    else
+        let s:spf13_apply_config_mapping = g:spf13_apply_config_mapping
+    endif
+
     " Easier moving in tabs and windows
     " The lines conflict with the default digraph mapping of <C-K>
     " If you prefer that functionality, add the following to your
@@ -1190,8 +1206,8 @@
         execute bufwinnr(".vimrc.local") . "wincmd w"
     endfunction
      
-    noremap <leader>ev :call <SID>EditSpf13Config()<CR>
-    noremap <leader>sv :source ~/.vimrc<CR>
+    execute "noremap " . s:spf13_edit_config_mapping " :call <SID>EditSpf13Config()<CR>"
+    execute "noremap " . s:spf13_apply_config_mapping . " :source ~/.vimrc<CR>"
 " }
 
 " Use fork vimrc if available {

.vimrc.before

@@ -92,6 +92,10 @@
     " Require a special keypress to enter multiple cursors mode
     "   let g:multi_cursor_start_key='+'
 
+    " Mappings for editing/applying spf13 config
+    "   let g:spf13_edit_config_mapping='<leader>ev'
+    "   let g:spf13_apply_config_mapping='<leader>sv'
+    
 " }
 
 " Use fork before if available {