Allow custom filter classes and fix multiple filter annotations

[onlime]

Previously, only a single @Filter annotation was possible. If you added multiple @Filter annotations to the same entity property, only the first one was honored, the others got ignored. You might also add a test for this.
Next to the default Zend\Filter classes, we should also allow our own custom app/bundle specific filter classes that extend Zend\Filter\AbstractFilter.

[codecov-io]

Current coverage is 100.00%

Merging #1 into master will not affect coverage as of c658ad4

@@            master      #1   diff @@
======================================
  Files            7       7       
  Stmts           91      91       
  Branches         0       0       
  Methods         21      21       
======================================
  Hit             91      91       
  Partial          0       0       
  Missed           0       0       

Review entire Coverage Diff as of c658ad4

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[Bukashk0zzz]

I will merge this and than add tests. Also I remove changes from .gitignore because some of folders must be ignored in your local global gitignore (https://insight.sensiolabs.com/what-we-analyse/git.user_specific_ignored_file)

[onlime]

Thanks a lot for the merge and the great test coverage in 1.0.1. Sorry about the changes in .gitignore - you're absolutely right. Nice you have pointed me to the global gitignore which I was actually using but completely forgot about.