iAppConfig: getValueType() get data from lexicon if available

[ArtificialOwl]

Enforce the correct value type when setting a config (via occ) defined in the Lexicon:

$ ./occ config:app:set my_app enable_something --value 'not_a_boolean'

In SetConfig.php line 194:
                                                        
  Value is not a boolean, please use 'true' or 'false'  

[come-nc]

There were 14 failures:

[ArtificialOwl]

There were 14 failures:

my bad, better detection of the presence of an entry in the Lexicon
should be better now

(squashed+pushed)