Added 'Exclude Sale Products' option to coupons

Added exclude sale products functionality based of the 'exclude product
ids' functionality in wc-coupon/wc-cart.

Compares product ID's in cart vs ID's in the array
'woocommerce_get_product_ids_on_sale'
idiotic missed semicolon

I cannot brain today, I has the dumb.
ditto
Updated everything so it actually works rather than fails hard

I messed up badly on the original with inheritance of variables, and
after a lot of issues realised that strict matching was necessary due
to the '0' string in woocommerce_get_products_on_sale()

Not hard to tell I am new to php.

Regardless this now functions as intended, stopping discount from being
applied to products with active sale prices or carts with items on sale
inside them.
Reset, please ignore

Long Story.
Revert "Reset, please ignore"

This reverts commit 3e59e64da3e8cb012d9301f8668a8ad58f7d9430.
Revert "Updated everything so it actually works rather than fails hard"

This reverts commit 2379a3a1bbc285a27a85905e8d0250b3c054079c.
Revert "ditto"

This reverts commit 0818bb055e1d569eaeaa0ea6b7f3a743181e9672.
Revert "idiotic missed semicolon"

This reverts commit 4c1f80b23de297117ed7292c602a20c5edf8f834.
Revert "Added 'Exclude Sale Products' option to coupons"

This reverts commit b763c7449a94d6fb3cb73a34300de4f3ca182d0c.
#2311 Fix for 'Exclude sale items from coupon'

included a checkbox on the coupon writepanel for the option

Had issues originally, worked out the in_array() needed to be a strict
type as woocommerce_get_product_ids_on_sale() has a '0' string in it.

Tested using 3.5.1 + git clone of WooCommerce
removed unnecessary line
Merge pull request #2313 from aj-adl/master

#2311 fix for "Exclude sale items from coupons"