[#SVCS-86] Add papaya renderer for NifTI and DICOM files.

Add customization to papaya library to disallow opening of new files from user desktop.

Consulted with Product Team. They determined that it would be confusing
and possibly dangerous to allow opening of files from user desktop, when
they might confuse it with the WaterButler repository.

Used a custom built papaya.js built on

https://github.com/TomBaxter/Papaya/tree/feature/noNewFiles

I have sent them a PR, hopefully they bite.

rii-mango/Papaya#101

Author: TomBaxter

mfr/extensions/papaya/__init__.py

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+from .render import PapayaRenderer  # noqa

mfr/extensions/papaya/render.py

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+import os
+import time
+import shutil
+
+from mako.lookup import TemplateLookup
+
+from mfr.core import extension
+from mfr.extensions import settings as ext_settings
+from mfr.extensions.papaya import settings
+
+
+class PapayaRenderer(extension.BaseRenderer):
+
+    data_dir = settings.DATA_DIR
+    data_old = settings.DATA_OLD
+    comp_ext = ext_settings.COMPRESSED_EXT
+
+    TEMPLATE = TemplateLookup(
+        directories=[
+            os.path.join(os.path.dirname(__file__), 'templates')
+        ]).get_template('viewer.mako')
+
+    def render(self):
+        self.remove_old_files()
+        file_name = os.path.basename(self.file_path)
+        if self.metadata.ext in self.comp_ext.keys():
+            second_ext = '.{}'.format(self.metadata.name.split('.')[-1])
+            if second_ext in self.comp_ext[self.metadata.ext]:
+                file_name = file_name + second_ext
+        file_name = file_name + self.metadata.ext
+        shutil.copyfile(self.file_path, self.data_dir + file_name)
+        return self.TEMPLATE.render(base=self.assets_url, file_name=file_name)
+
+    def remove_old_files(self):
+
+        for data_file in os.listdir(self.data_dir):
+            if data_file == '.gitignore':
+                continue
+            if (time.time() - os.path.getctime(self.data_dir + data_file)) >= self.data_old:
+                os.unlink(self.data_dir + data_file)
+
+    @property
+    def file_required(self):
+        return True
+
+    @property
+    def cache_result(self):
+        return True

mfr/extensions/papaya/settings.py

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+from mfr import settings
+
+config = settings.child('PAPAYA_EXTENSION_CONFIG')
+
+# Directory to temporarily store papaya image files
+DATA_DIR = 'mfr/extensions/papaya/static/data/'
+# Files older then this many seconds will be deleted from DATA_DIR at the beggining of each render.
+DATA_OLD = 300

mfr/extensions/papaya/static/README-papaya.txt

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+Currently using a custom built papaya.js with option to remove the ability to open new files from the users desktop.
+
+https://github.com/TomBaxter/Papaya/tree/feature/noNewFiles
+
+I have sent them a PR, hopefully they bite.
+
+https://github.com/rii-mango/Papaya/pull/101

mfr/extensions/papaya/static/data/.gitignore

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+# Ignore everything in this directory
+*
+# Except this file
+!.gitignore