WIP

In Go world development workflow is organized around so-called workspace
where multiple packages can be installed / worked on etc. The following
page describes Go workspaces:

https://golang.org/doc/code.html

A new [gowork] section and infrastructure around it is introduced.
Quoting code:

    # gowork is a top-level section representing workspace
    #
    # users should add `install` field to [gowork] to describe packages they want to
    # be installed (+ automatically their dependencies are installed too). e.g.
    #
    #   [gowork]
    #   install =
    #       lab.nexedi.com/kirr/neo/go/...  \
    #       github.com/pkg/profile          \
    #       golang.org/x/perf/cmd/benchstat

The way it all works inside is:

- gowork organizes to create go.work/ directory in buildout root
- inside it creates env.sh which when sources in shell adjusts all paths
  so that appropriate go compiler is in path, GOPATH is also set
  appropriately, etc - in other words everything needs for using/working
  on this workspace is setup in the environment.
- in actual user software profile the list of Go projects which needs to
  be installed by SlapOS has to be listed. The [gowork] machinery takes
  care about git-cloning these projects and `go install`s them after.
- by SlapOS design builds have to be reproducible and so every component
  state/version has to be fixed.

  A convenient helper (gowork-snapshot) to get snapshot of git go
  packages installed with their exact revisions is added. This should be
  used to automatically (re-)generate list of go git repositories &
  their pinning for a workspace.

For a new Go project that needs to be slaposified the workflow should be:

- first get a project into working state via any convenient way (`go get`, etc.)
- generate list of go packages & their pinning with gowork-snapshot
- extend golang/buildout.cfg and in project software profile add

	[gowork]
  	install = your-top-level-packages

  as it was outlined above.

P.S.

[golang] is removed because

1. it is not used anywhere in slapos.git tree, and
2. the canonical way to work on go projects from now on will be to use
   [gowork]. There latest go version is preconfigured, but users can
   override it to some particular other version in their projects as they
   need.

/reviewed-on	 nexedi/slapos!242
/also-needed-for nexedi/slapos!243

This reverts merge request !243

The first proof of concept  of Caddy in Slapos. 

For now, everything is inside software/caddy but in the next merge request we will move to stack. 

@rafael @romain 


/reviewed-on !243

WIP

  Environment requires new lines instead spaces

   This is required got the usage of git

  MD5SUM update was missing.

Experimental. Not automatically executed.

Restores given backup, configures service as a slave to given master,
starts replication.

Like for "normal" backup restoration, any running mariadb is killed,
started with backup-restoration-friendly parameters, and killed again once
restored.

As there is AFAIK no way to ask supervisor to start even one of our own
services, this script unfortunately leaves the partition in a
not-immediately useful state.

Nothing references this section otherwise.

This value is supposed to come from configuration file, which is already
implicitly provided inside used wrapper.