Merge aegir_http_basic module

Lets consolidate some modules to improve the Aegir ecosystem.

I've mentioned this before on the aegir mailinglist... Now it's merged in here. and in provision_tasks_extra.

Remaining tasks:
- Documentation
- Release notes
- update http://community.aegirproject.org/contrib-modules
- Cleanup the old module on github, and the pull request

Technical:

cd aegir_http_basic/
git subtree split --prefix=provision --branch=aegir_http_basic-provision
git subtree split --prefix=hosting --branch=aegir_http_basic-hosting

cd ../hosting_tasks_extra
git remote add aegir_http_basic ../aegir_http_basic/
git fetch
git subtree add --prefix=http_basic_auth 70d2fa79ef4a42ce5c8b52950bae2fe3d49248e2

cd ../provision_tasks_extra/
git remote add aegir_http_basic ../aegir_http_basic/
git fetch
git subtree add --prefix=http_basic_auth 6697f05cc7840846baf5194f2c7f3a072024dc1b