Don't lose filter priority when merging two Filter Chain
Allow to set the filter priority in the config array passed to the factory
Merge branch 'hotfix/4216'

Close #4216
Fixes #3908
Add Filter\FilterChain unit test to test if filter priorities are kept when merging one filterChain into another.
Add InputFilter\Factory unit test to check that the priority setting in the filters key array are passed to the FilterChain
Merge pull request #4148 from leup/filterspriority

Filters priority setting when populating filters in inputfilter factory and not losing it when merging filter chains
[#4148] CS fixes

- per php-cs-fixer
Merge branch 'hotfix/4148' into develop

Forward port #4148