Tidied up SimpleXmlWriter to prepare for refactoring
Changed SimpleXmlWriter to call process only once per record.
Output a new-line before the final footer tag.
PicaEncoder implemented

The PicaEncoder encodes the "Record-Field-Subfields" Stream into pica+
Format. If there are S-subfields in the input stream which is processed
by PicaDecoder (by default) it will be not able to encode them to
original format (because of lost of data during the decoding). In this
case, the decoder should use the option appendControlSubField="false" to
keep the original data.
The #111 Requests are implemented.
The field and subfield names are check by pattern now.
The sequences of the stream elements are controlled and it must be
nested structured.
Fix issue #115: WellFormednessChecker should check for null in ids.

Added a check for null record ids to the WellFormednessChecker.
Added tests for WellformednessChecker.
Unified capitalisation of WellformednessChecker.
Fixes for modules and tests that used null as record id.
The source code is optimized.
The changes make the code more readable.
Some unnecessary checks are deleted.
Merge branch 'adding-pica-encoder' of http://github.com/liyining/metafacture-core into liyining-adding-pica-encoder
Nested entities will be checked now.
The javadoc about the S (control) subfield is still there, but the
newest core does not support its processing.
Merge branch 'adding-pica-encoder' of http://github.com/liyining/metafacture-core into liyining-adding-pica-encoder
Minor clean-up
Adds a module to filter consecutive duplicated objects.
Merge pull request #117 from ah641054/eliminate-duplicate-triples

Adds a module to filter consecutive duplicated objects.
Add `@Out(Void.class)` annotations to writer implementations

The IDE uses the `@In` and `@Out` annotations to validate workflows.
It issues warnings when no annotation is found. Since the writers
don't actually output anything as part of the workflow, `Void.class`
might make sense as their output type.
resolved #120
Merge branch 'master' of ssh://github.com/culturegraph/metafacture-core
#110 fixed