[#4761] Convert exceptions to warnings

- To retain BC, filters should never raise exceptions
- Instead, raising warning and returning original value
[#4761] Added tests for null values

- null values should be filtered without warnings
[#4761] null values should not raise warnings

- null values should not be filtered, and should not raise warnings
[#4766] wrote tests to indicate behavior is opt-in

- Added `setUseIncludePath()` call to translator adapters
- added flag, Factory::USE_INCLUDE_PATH, as second argument to config
  factory
[#4766] Config makes include_path usage opt-in only

- You must pass the `$useIncludePath` to either `fromFile()` or
  `fromFiles()` for it to be used. Constants were created with boolean
  values for those using IDEs.
[#4766] Make include_path abilities opt-in in Translators

- Created AbstractFileLoader, which provides implementation details for
  when/how to use the include_path to load translation file assets.
- Updated INI, gettext, and PHP loaders to extend AbstractFileLoader.
[#4766] Add docblock detailing how to set include_path flag

- Added to translator loader plugin manager
Remove constants

- Remove constants, per @DASPRiD
Add Config\Reader for Java-style properties
Add unit tests and test assets for Zend\Config\Reader\JavaProperties
Conform to ZF2 contribution coding standards
Fix unit tests for invalid properties
Support use of the exclamation point "!" as comment mark
Fix indentation and eof newline for code standards
Fix docblock tags
Fixed spacing with php-cs-fixer
Removed namespace alias
Removed confusing lines from test assets
Fixed spacing in parse method
Clarified test for invalid include in string