Remote call trigger support (#105)

* add support of remote task tracking
* add remote call trigger implementation
* docs update
* add cross-service upload
* add notes about user
* add more ability to control upload
* multipart upload with signatures as well as safe file save
* configuration reference update
* rename watcher methods
* erase logs based on current package version

Old implementation has used process id instead, but it leads to log
removal in case of remote process trigger

* add --server flag for setup command
* restore behavior of the httploghandler

Dockerfile

@@ -11,6 +11,7 @@ ENV AHRIMAN_PACKAGER="ahriman bot <ahriman@example.com>"
 ENV AHRIMAN_PACMAN_MIRROR=""
 ENV AHRIMAN_PORT=""
 ENV AHRIMAN_REPOSITORY="aur-clone"
+ENV AHRIMAN_REPOSITORY_SERVER=""
 ENV AHRIMAN_REPOSITORY_ROOT="/var/lib/ahriman/ahriman"
 ENV AHRIMAN_UNIX_SOCKET=""
 ENV AHRIMAN_USER="ahriman"