Remove backticks from CREATE TABLE SQL.

These are not supported by dbDelta and cause a Notice. Fixes #2781.
Merge pull request #2782 from jjeaton/create-table-notice

Remove backticks from CREATE TABLE SQL.
change default item count in [downloads] shortcode from 10 to 9 - #2785
Merge pull request #2786 from sdavis2702/master

change default item count in [downloads] shortcode from 10 to 9 - #2785
Make sure discount code exists before trying to apply it

Checks that the discount code exists before trying to apply it, otherwise `edd_get_discounted_amount()` will return `0`.

When this is then subtracted from `$price` and inverted to make `$discounted_price` here:

`$discounted_price -= $price - edd_get_discounted_amount( $discount, $price );`

 it'll always equal the negative value of the price giving the user a 100% discount.
Merge pull request #2791 from lukechilds/patch-2

Make sure discount code exists before trying to apply it
Fix some coupon insert hooks + prevent notices
Merge branch 'JeroenSormani-master'
Merge branch 'master' into release/2.2