First Pass at Inline Documentation for EDD Filters

includes\class-edd-api.php
Minor spelling error
Merge pull request #2030 from NikV/master

First Pass at Inline Documentation for EDD Filters
only validate IPN when it's enabled. Closes #2032
remove echo test. #2032
Actually pass backtrace to trigger_error(). Avoids just being presented with an error saying "1"
Merge pull request #2034 from leewillis77/print_r_fix

Actually pass backtrace to trigger_error().
Merge pull request #2029 from ghost1227/issue/1988

Minor spelling error
don't prevent sessions in admin. #2031
Update column 'download' to use singular label
Merge pull request #2039 from elliott-stocks/patch-10

Update column 'download' to use singular label
Account for UPLOADS constant in process-download.php. #2041
Merge branch 'master' of github.com:easydigitaldownloads/Easy-Digital-Downloads
Add https support to get_option('siteurl')
Fixed str_replace() error
Allow state_rate to be 0
Revert
Merge pull request #2044 from wpsmith/bug/2026

Bug/2026, allow state_rate to be 0
spanish translation modification
es_ES.po to see modified strings