tapper init: provide a subdir for producers

...to make a decision easier to the user.
tapper init: testplans/ subdir now fine-grained

The ~/.tapper/testplans/ subdir is expected to be used
by the user. To make it easier to provide updates we
now initialize our bundled testplans file-by-file.

Now the user doesn't need to delete the whole directory
to get our bundled new testplan files.
testplans/*/local: allow specifying precondition producers
testplans/*/example03-builder: frontend to testplans/*/local

...to demonstrate arguments to a producer.

An example precondition producer which builds a
file and provides preconditions pointing to the
built file.
example_producer_builder.sh: example for builder

An example precondition producer which builds a
file and provides preconditions pointing to the
built file.
example_kernel_install.sh: example installer

...used inside the produced YAML produced from the
producer 'example_producer_builder.sh'.
changelog++
v4.1.8

        - helloworld: example_kernel_install.sh: example installer
        - helloworld: example_producer_builder.sh: example for builder
        - helloworld: testplans/*/example03-builder: frontend to testplans/*/local
        - helloworld: testplans/*/local: allow specifying precondition producers
        - tapper init: testplans/ subdir now fine-grained
        - tapper init: provide a subdir for producers
        - add notifications for new testrun if requested
        - [TEST] adding notification with testrun
        - [FIX] API docs: new notifications can not be added as a string
Use iterator instead of ->all()

Using an iterator is more ressource friendly.
[RFK] rewrite Cmd::Testplan to meet Cmd requirements

Cmd::Testplan did have lots of CLI functionality in it. This should not
be because Cmd is used by WebGUI too. This patch reworks the testplan
Cmd to meet the requirements for Cmd modules.
[FEAT] query function for testplans

cr https://cr.amazon.com/r/1620776/
queue delete changes
 - support of parameter queue object instead of queue id
 - add missing feature "force"
add_host() now support host_id and hostname
revoke changes: add_host() now support host_id and hostname ... wrong
repository
add_host() now support host_id and hostname
do not die for notification insert
cr https://cr.amazon.com/r/1645332/
- add additional support of Queue-Objects for update()
- add filling of column updated_at to update()
- modify wrong comment
- bugfix creation of notify messages for testruns
Tapper::Cmd::Testrun->add return instead of print error string
[TEST] uncommited files for testplan test

These files belong to a test commited with commit
c266b7ade15f2f7bb4273d2ceba1a1744c54a02f.