automatically bump pkgrel on version duplicates

The new --(no-)increment flag has been added to add, update and rebuild
subcommands. In case if it is true and package version is the same as in
repository, it will automatically bump pkgrel appending (increasing)
minor part of it (e.g. 1.0.0-1 -> 1.0.0-1.1).

Inn order to implement this, the shadow (e.g. it will not store it in
database) patch for pkgrel will be created

.readthedocs.yaml

@@ -21,4 +21,3 @@ python:
         - docs
         - s3
         - web
-  system_packages: true