Add datastore filter to backup-list

This fix enhances the backup-list command to optionally receive
a datastore name or ID to filter the backup list by. The filter
is sent as a query string.

To attach the query string to the URL and have it still work with
the URL for pagination, i have made some changes in the way url
with query strings are constructed. This includes the pagination
URL.

partially implements: blueprint backup-metadata

Change-Id: I0b9ef3ec7f51ed76517a22f9c0edfdce3694a36f
Added optional marker/limit to list command

The trove client did not allow you to pass in a marker or limit
for list instances.  These arguments are now allowed, and the
resulting list filtered accordingly.  Both arguments are optional.

Change-Id: I7cb697d57d11f72c0349fbe50c48d8b33593721b
Closes-Bug: #1294950
Overwrite HelpFormatter constructur to extend argument column

Overwrite the HelpFormatter constructor in the class
OpenStackHelpFormatter to modify the default value of the
max_help_position to extend the width of the argument column
in the help output.

example output before this patch:

    configuration-attach
                        Attaches a configuration group to an instance.
    configuration-create
                        Creates a configuration group.
    configuration-default
                        Shows the default configuration of an instance.
    configuration-delete
                        Deletes a configuration group.
    configuration-detach
                        Detaches a configuration group from an instance.

example output after this patch:

    configuration-attach          Attaches a configuration group to an
                                  instance.
    configuration-create          Creates a configuration group.
    configuration-default         Shows the default configuration of an
                                  instance.
    configuration-delete          Deletes a configuration group.
    configuration-detach          Detaches a configuration group from an
                                  instance.

Change-Id: Ia3ad8e9fefca6da40f55ab3de902c015a0d17006
Closes-Bug: #1326471
Merge "Add datastore filter to backup-list"
Merge "Overwrite HelpFormatter constructur to extend argument column"
Merge "Added optional marker/limit to list command"