Fix validation errors in example document.

Closes #115.

examples/dataset/full.jsonld

@@ -4,16 +4,19 @@
  },
  "@id": "http://lod.example-data-repository.org/id/dataset/3300",
  "identifier": {
+ "@type": "PropertyValue",
  "propertyID": "https://registry.identifiers.org/registry/doi",
  "value": "doi:10.1234/1234567890",
  "url": "https://doi.org/10.1234/1234567890"
  },
+ "sameAs": "https://doi.org/10.1234/1234567890",
+ "isAccessibleForFree": true,
  "url": "https://www.example-data-repository.org/dataset/3300",
  "@type": "Dataset",
  "name": "Larval krill studies - fluorescence and clearance from ARSV Laurence M. Gould LMG0106, LMG0205 in the Southern Ocean from 2001-2002 (SOGLOBEC project)",
  "alternateName": "larval krill pigments",
  "description": {
- "@type": "HTML",
+ "@type": "Text",
  "@value": "<p>"Winter ecology of larval krill: quantifying their interaction with the pack ice habitat"</p>\r\n\r\n<p>The goal of the larval krill studies was to investigate the physiology and ecology of krill larvae associated with the pack ice and the microbial community on which they feed.</p>\r\n\r\n<p>During LMG0106 we occupied two 4-5 day ice stations (Robert and Billy) and sampled several other ice floes opportunistically. We conducted 10 instantaneous growth rate experiments, and 4 whole body clearance time experiments to determine gut passage time (decline in pigment content over time). We also sampled larvae at two additional sites for initial body pigment content (whole body fluorescence), and at 4 sites for condition factor. The under-ice algal community was sampled at one site. Length and stage frequency determinations were also determined.</p>\r\n\r\n<p>We occupied three time-series stations of approximately 1 week each, and in addition opportunistically sampled at times when other activities had priority. Our primary goal during the cruise was to occupy three ice camps or process stations with the intent of thoroughly studying the under-ice environment by SCUBA in conjunction with other projects working topside. <a href="http://www.ccpo.odu.edu/Research/globec/main_cruises02/lmg0205/report_lmg0205.pdf" target="_blank"><em>(from cruise report LMG0205)</em></a></p>"
  },
  "datePublished": "2010-02-03",