Rename package from 'nw' to 'novelwriter' (#868)

* Rename nw folder to novelwriter
* Rename nw to novelwriter in auxiliary files
* Rename nw to novelwriter in main app source
* Rename nw to novelwriter in tests
* Make setup script for pdf docs less spammy

novelwriter/assets/icons/typicons_grey_dark/download.svg

@@ -0,0 +1,31 @@
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+   width="24"
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+        <dc:format>image/svg+xml</dc:format>
+        <dc:type
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+        <dc:title></dc:title>
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