Coding Standards: Main plugin file

* fixed indentation - swapped spaces for tabs at start of line, swapped
tabs for spaces min-line for alignment
* removed instances of `@return void` and `@access public`

@see http://make.wordpress.org/core/handbook/coding-standards/php/
Coding Standards: Abstract classes

* fixed indentation - swapped spaces for tabs at start of line, swapped
tabs for spaces min-line for alignment
* removed instances of `@return void` and `@access public`
* improved readability

@see http://make.wordpress.org/core/handbook/coding-standards/php/
Coding Standards: Less files

* fixed indentation - swapped spaces for tabs at start of line, swapped
tabs for spaces min-line for alignment
Coding Standards: Admin JS

Fixed spacing as per
http://make.wordpress.org/core/handbook/coding-standards/javascript/
Coding Standards: Admin - Importers

* fixed indentation - swapped spaces for tabs at start of line, swapped
tabs for spaces min-line for alignment
* removed instances of `@return void` and `@access public`
* improved readability

@see http://make.wordpress.org/core/handbook/coding-standards/php/
Coding Standards: Admin - Meta boxes

* fixed indentation - swapped spaces for tabs at start of line, swapped
tabs for spaces min-line for alignment
* removed instances of `@return void` and `@access public`
* improved readability

@see http://make.wordpress.org/core/handbook/coding-standards/php/
Coding Standards: Admin - Reports

* fixed indentation - swapped spaces for tabs at start of line, swapped
tabs for spaces min-line for alignment
* removed instances of `@return void` and `@access public`
* improved readability

@see http://make.wordpress.org/core/handbook/coding-standards/php/
Coding Standards: Admin - Settings

* fixed indentation - swapped spaces for tabs at start of line, swapped
tabs for spaces min-line for alignment
* removed instances of `@return void` and `@access public`
* improved readability

@see http://make.wordpress.org/core/handbook/coding-standards/php/
Improved .editorconfig for *.json and *.md
Add WC_Abstract_Order::is_editable()

To centralise logic used to determine if an order can be edited from
the Edit Order screen
Add 'wc_order_is_editable' filter
Store order's editable status in property

To save overhead of a function call
fixed some docblocks
Add a link to PayPal's guide on API Creds
Merge pull request #6152 from shivapoudel/patch-1

Improved .editorconfig for *.json and *.md
Merge pull request #6155 from thenbrent/paypal_api_creds_help

Add a link to PayPal's guide on API Creds
Merge pull request #6154 from thenbrent/is_editable

Add `WC_Abstract_Order::is_editable()` method and `'wc_order_is_editable'` filter
Remove $can_be_edited in favour of ->is_editable()

For #6154
Remove redundant wc_order_can_be_edited filter

#6154
updated the language files