When the app has an AccountSessionModule and the account is logged in, default the email address.

We do this manually on all our sites, so let's do it here.
Default the user's email address in build.

Prior version would override any submmitted values. Thanks @gauthierm for pointing it out.
Only default the email address in load.

This takes advantage of SiteEditPage's load only being called f the form is not processed and prevents the defaulting from overwriting the value.
Treat all contact forms as not new so the defaulting of the email address works correctly.
better method name and call parent::load()
Merge pull request #70 from isaacgrant/contact-email-address-init

When the app has an AccountSessionModule and the account is logged in, default the email address.