NEXUS-7345: add nexus-commands bundle+feature

https://issues.sonatype.org/browse/NEXUS-7345
http://bamboo.s/browse/NX-OSSF371-1 :white_check_mark: 

```
karaf@root()> connect plocal:../sonatype-work/nexus/db/config admin admin

Connecting to database [plocal:../sonatype-work/nexus/db/config] with user 'admin'...OK

karaf@root()> listclasses 

CLASSES
----------------------------------------------+------------------------------------+------------+----------------+
 NAME                                         | SUPERCLASS                         | CLUSTERS   | RECORDS        |
----------------------------------------------+------------------------------------+------------+----------------+
 capability_capabilitystorageitem             |                                    | 11         |              1 |
 componentsource                              |                                    | 9          |              1 |
 OFunction                                    |                                    | 6          |              0 |
 OIdentity                                    |                                    | -          |              0 |
 ORestricted                                  |                                    | -          |              0 |
 ORIDs                                        |                                    | 8          |              0 |
 ORole                                        | OIdentity                          | 4          |              3 |
 OSchedule                                    |                                    | 7          |              0 |
 OTriggered                                   |                                    | -          |              0 |
 OUser                                        | OIdentity                          | 5          |              3 |
 viewconfig                                   |                                    | 10         |              2 |
----------------------------------------------+------------------------------------+------------+----------------+
 TOTAL = 11                                                                                                   10 |
----------------------------------------------+------------------------------------+------------+----------------+

karaf@root()> listclusters 

CLUSTERS
----------------------------------------------+-------+-------------------+----------------+
 NAME                                         | ID    | CONFLICT STRATEGY | RECORDS        |
----------------------------------------------+-------+-------------------+----------------+
 capability_capabilitystorageitem             |    11 |                   |              1 |
 componentsource                              |     9 |                   |              1 |
 default                                      |     3 |                   |              0 |
 index                                        |     1 |                   |              6 |
 internal                                     |     0 |                   |              3 |
 manindex                                     |     2 |                   |              1 |
 ofunction                                    |     6 |                   |              0 |
 orids                                        |     8 |                   |              0 |
 orole                                        |     4 |                   |              3 |
 oschedule                                    |     7 |                   |              0 |
 ouser                                        |     5 |                   |              3 |
 viewconfig                                   |    10 |                   |              2 |
----------------------------------------------+-------+-------------------+----------------+
 TOTAL = 12                                                               |             20 |
------------------------------------------------------+-------------------+----------------+

karaf@root()> select from componentsource

----+----+-------------+--------------+-------------------------+-------------------------------------
#   |@RID|name         |id            |factoryName              |configuration                        
----+----+-------------+--------------+-------------------------+-------------------------------------
0   |#9:0|binary-source|foo_2f32wdf23r|RawComponentSourceFactory|{remote-url=http://search.maven.org/}
----+----+-------------+--------------+-------------------------+-------------------------------------

1 item(s) found. Query executed in 0.001 sec(s).
```