Improve the citations list

[jhlegarreta]

The citations list in here requires some work:

• The encoding of some characters is incorrect (see the question mark diamond characters in johnson2015itk for example)
• The keys to the publications are not consistent, like "authorYearVenue" (e.g. beare2011citk, RN826).
• Some fields do not have any meaningful information (e.g. https://github.com/InsightSoftwareConsortium/insightsoftwareconsortium.org/blob/master/static/citations-visualization/ITKBibliography.bib#L72)
• The entries for each type should be the same and complete, and be sorted in the same way for the sake of readability.
• The publications in the To Appear category (see https://insightsoftwareconsortium.org/citations) were surely published by now. These entries need to be updated.
• It is probably best to remove the abstracts, as they take up a non-negligible amount of space that makes it difficult navigating across the file.
• Not sure about how the type field (e.g. https://github.com/InsightSoftwareConsortium/insightsoftwareconsortium.org/blob/master/static/citations-visualization/ITKBibliography.bib#L71) is used; for most cases the BibTeX entry type already defines the type, so best may be to leave it blank everywhere for the sake of consistency (?).
• The articles listed in the ITK README should be consistent to the data in the list or added if missing.