Adding JSON-LD 1.1 support (only writer)

[samubura]

This should be working fine and converting from the TDModel to a JSON-LD 1.1 representation.
Still need to test a few things that we can maybe discuss together.

[codecov]

Codecov Report

Merging #56 (945f086) into master (886ec3f) will increase coverage by 1.16%.
The diff coverage is 91.52%.

@@             Coverage Diff              @@
##             master      #56      +/-   ##
============================================
+ Coverage     83.49%   84.65%   +1.16%     
- Complexity      256      338      +82     
============================================
  Files            30       35       +5     
  Lines          1018     1245     +227     
  Branches        119      141      +22     
============================================
+ Hits            850     1054     +204     
- Misses          114      125      +11     
- Partials         54       66      +12     

Impacted Files	Coverage Δ
...eractions/wot/td/affordances/ActionAffordance.java	100.00% <ø> (ø)
...actions/wot/td/affordances/PropertyAffordance.java	100.00% <ø> (ø)
.../ch/unisg/ics/interactions/wot/td/io/TDWriter.java	33.33% <33.33%> (ø)
...nisg/ics/interactions/wot/td/ThingDescription.java	68.04% <66.66%> (-0.05%)	⬇️
...ch/unisg/ics/interactions/wot/td/io/json/JWot.java	75.00% <75.00%> (ø)
.../ics/interactions/wot/td/schemas/ObjectSchema.java	85.45% <75.00%> (ø)
.../interactions/wot/td/io/json/SchemaJsonWriter.java	82.22% <82.22%> (ø)
.../ics/interactions/wot/td/io/json/TDJsonWriter.java	92.98% <92.98%> (ø)
...nisg/ics/interactions/wot/td/affordances/Form.java	90.90% <100.00%> (ø)
...ions/wot/td/affordances/InteractionAffordance.java	87.50% <100.00%> (ø)
... and 11 more

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