migrate to tox

this also requires to move default configuration files to share/ahriman.
Thus the following features have been added
* default configuration is not stored in /usr/share/ahriman/settings
* package installed via PKGBUILD now copies files from /usr
* configuration class now fallbacks to default in /usr

package/share/ahriman/settings/ahriman.ini

@@ -0,0 +1,62 @@
+[settings]
+include = ahriman.ini.d
+logging = ahriman.ini.d/logging.ini
+
+[alpm]
+aur_url = https://aur.archlinux.org
+database = /var/lib/pacman
+repositories = core extra community multilib
+root = /
+
+[auth]
+target = disabled
+max_age = 604800
+oauth_provider = GoogleClient
+oauth_scopes = https://www.googleapis.com/auth/userinfo.email
+safe_build_status = yes
+
+[build]
+archbuild_flags =
+build_command = extra-x86_64-build
+ignore_packages =
+makechrootpkg_flags =
+makepkg_flags =
+
+[repository]
+name = aur-clone
+root = /var/lib/ahriman
+
+[sign]
+target =
+
+[report]
+target = console
+
+[console]
+use_utf = yes
+
+[email]
+full_template_path = /usr/share/ahriman/templates/repo-index.jinja2
+no_empty_report = yes
+template_path = /usr/share/ahriman/templates/email-index.jinja2
+ssl = disabled
+
+[html]
+template_path = /usr/share/ahriman/templates/repo-index.jinja2
+
+[upload]
+target =
+
+[rsync]
+command = rsync --archive --compress --partial --delete
+
+[s3]
+chunk_size = 8388608
+
+[web]
+debug = no
+debug_check_host = no
+debug_allowed_hosts =
+host = 127.0.0.1
+static_path = /usr/share/ahriman/templates/static
+templates = /usr/share/ahriman/templates