Xliff 1.2 serializer

[dragosv]

Xliff 1.2 Serializer that is meant to be extended using the apply_xslt plugin (#77)

[codecov-io]

Codecov Report

Merging #78 into master will increase coverage by 0.58%.
The diff coverage is 79.82%.

@@            Coverage Diff             @@
##           master      #78      +/-   ##
==========================================
+ Coverage   50.95%   51.54%   +0.58%     
==========================================
  Files          89       90       +1     
  Lines        6727     6841     +114     
  Branches     1696     1718      +22     
==========================================
+ Hits         3428     3526      +98     
- Misses       2646     2655       +9     
- Partials      653      660       +7

Impacted Files	Coverage Δ
lib/Serge/Engine/Plugin/serialize_xliff.pm	79.82% <79.82%> (ø)
lib/Serge/DB.pm	65.7% <0%> (+0.52%)	⬆️
lib/Serge/DB/Cached.pm	62.92% <0%> (+1.7%)	⬆️

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[dragosv]

In order to understand the way the xliff serializer is intended to be used (apply_xslt on before_deserialize_ts_file and after_serialize_ts_file) take a look at https://github.com/dragosv/serge/tree/xliff_full (tests on apply_xslt). Will pull request this branch as well, once both dependent pull request are merged.

[dragosv]

To be more explicit, xliff support differs between translation providers, requiring all kinds of changes. The two big variations are either needing resname on the trans-unit element or only supporting the id attribute and just the very basic xliff implementation (just source, target and note elements).

[iafan]

Looks like you changed the entire file from CRLF to LF. While this might be a welcome change by itself, it's not a part of the PR.

[dragosv]

Fixed.