WIP: refactor: modular filters

[miurahr]

This is topic development branch to demonstrate how filters can be modules.

Pull request type

• Other (describe below) refactor

Which ticket is resolved?

What does this PR change?

• All of #931 changes
• Split filters into three modules, filters2, staxfilters (from filters4) and xmlfilters (from filters3).
• Refactor tests into each modules.

Other information

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[miurahr]

Now modularization of filters have been almost done.

What I have done is...

• Change all filters to be OmegaT 3.1 interface that have loadPlugin method.
• Refactor source and test code under sub project, filters2 and xmlfilters
• xmlfilters project has filters3 and filters4 filters
• Move test data under <subproject>/src/test/resources/
• Put .gitattributes for some test data which EoL is important
• Introduce testFixtures stub filters that are used in core test codes, which requires htmlparser and jackson dependency.
• Tweak dependency for filters. remove stax and PDF library from core and put in filters sub project
• Update checkstyle suppression configuration
• Update test cases to point new path of test data

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