is_email_receipt setting on recurring contribution should take precedence over contribution page setting

Basically the is_email_receipt gets set when you sign up for a recurring contribution page based on the contribution page (good) but if people choose to change this value (probably by code) then the BaseIPN class should respect that value. So, the setting on the contribution_recur record rather than on the contribution_page record is the correct one to use.

I have code for this.