BUG: fix/doc DMRIInstall (#6594)

* BUG: fix/doc DMRIInstall

Fixes #6593 by updating api and adding a .md doc.

* STYLE: fix lint indent error

Docs/user_guide/modules/dmriinstall.md

@@ -0,0 +1,20 @@
+# DMRI Install
+
+## Overview
+
+A helper for enabling DMRI functionality.  Historically, DMRI functionality was part of the Slicer core and some infrastructue was not easy to move to the extension.  This module helps users re-enable the full functionality.
+
+## Panels and their use
+
+
+- **Install SlicerDMRI**: Triggers the extension manager process.
+
+## Contributors
+
+- Isaiah Norton (BWH)
+- Lauren O'Donnell (BWH)
+- Steve Pieper (Isomics, Inc.)
+
+## Acknowledgements
+
+The SlicerDMRI developers gratefully acknowledge funding for this project provided by NIH NCI ITCR U01CA199459 (Open Source Diffusion MRI Technology For Brain Cancer Research), NIH P41EB015898 (National Center for Image-Guided Therapy) and NIH P41EB015902 (Neuroimaging Analysis Center), as well as the National Alliance for Medical Image Computing (NA-MIC), funded by the National Institutes of Health through the NIH Roadmap for Medical Research, Grant U54 EB005149.

Modules/Scripted/DMRIInstall/DMRIInstall.py

@@ -116,12 +116,10 @@ def onApply(self):
             self.applyButton.enabled = False
             return
 
-        md = emm.retrieveExtensionMetadataByName("SlicerDMRI")
-
-        if not md or 'extension_id' not in md:
+        extensionName = 'SlicerDMRI'
+        emm.interactive = False  # prevent display of popups
+        emm.updateExtensionsMetadataFromServer(True, True)  # update extension metadata from server now
+        if not emm.downloadAndInstallExtensionByName(extensionName, True, True):  # install dependencies, wait for installation to finish
             return self.onError()
 
-        if emm.downloadAndInstallExtension(md['extension_id']):
-            slicer.app.confirmRestart("Restart to complete SlicerDMRI installation?")
-        else:
-            self.onError()
+        slicer.app.confirmRestart("Restart to complete SlicerDMRI installation?")