To avoid the explosion of "if" structure, it is better replace it using
a "for" structure.

The behavior of the code still the same.

According to the previous commit:
  - 017a02ef

We just need to make sure that the new option is gonna be propagated to
Software class. Indeed, in the buildout command line as well.

The new parameter is:
  - upload_authentication_file: the content must be the path of
    SSL key which must be used to make the user authentication in the
    Networkcache HTTP server.

It must be propagated to buildout command line, of course.

The default value was ' ' because it was always being propagating to the
buildout command line. But since the commit
d8dca883, it does not happen anymore.

This option is only propagated to buildout command line if it is not
None.

Inside of slapos.cfg you can define the section called networkcache,
which should contain all the required configuration to upload files
to shacache and shadir.

Options:
  - upload-cache-url: url to upload content to shacache
  - upload-dir-url: url to upload content to shacache
  - signature-private-key-file: private key file used to sign the
    information which may be sent to shadir

Note: the option signature-private-key-file, may also be used as
parameter of slapgrid command.
   (i.e. --signature_private_key_file=/path/to/private.pem)

And of course, following the previous commit, we need to propagate these
parameters to Software class.

Added upload_cache_url and upload_dir_url:
 - upload_cache_url: the value must be the url of shacache used to
   upload
   content.
 - upload_dir_url: the value must be the url of shadir used to upload
   the
   information about the content.

Also, the signature_private_key_file is not required to instanciate a
Software object, then it can be None by default.

All these parameters listed above should only be used in the buildout
command line, if they are not None. And it should be defined under
networkcache-section.

By default the buildout's options are written with '-' instead of '_'.

So, lets keep like that.

Removed the argument signature_public_file because it should be inside
the software profile under networkcache-section.

And renamed signature_private_file to signature_private_key_file.

Title is humand related name of computer, and reference is used by SlapOS
configuration.

Use My Acccount web section to expose buttons to request and revoke certificate.
Move out credentials management to button.
Reuse existing WebSection_viewMyAccountRender.

This supports configuration, when bridge cannot be attached with IPv6 capable
interface (like a lot of WLAN interfaces and IPv6 tunnels).

Thanks to setting ipv6_interface in slapformat configuration file, IPv6
generation will be done there, but IPv4 will be still available on bridge.

Users shall be able to instantiate software instances on their computers. This
is the most often found scenario (add *my* computer and instantiate on *it*
some software).

Add condition to support dictionary. This fix was needed to support Slave Instance inside parameter_dict because each Slave Instance is one dictonary