Enhancements: macros, filters, API, and pre-commit

Also, drop unused templates/.gitignore and avatar.html

Change-Id: I2faa3ab8a33e0a48c47e3595c91976dd956a1535
Add projects pages

* projects/members_show.html
* projects/security_groups_edit.html
* projects/show.html

Change-Id: Idbfbdbbcf9d3981ce3549236c5c52451920cc962
Add settings pages

* settings/change_password.html
* settings/credentials.html
* settings/ssh_keys.html
* settings/ssh_keys_create.html

Change-Id: Ia33d7573509e2bbdce7cc7d80429982325a00136