Migrate to SQLCipher for messages/cache

Quite a few other fixes, including:
  - Sending to contact with no avatar yet (not synced from mobile)
  - Left pane doesn't update quickly or at all on new message
  - Left pane doesn't show sent or error status

Also:
 - Contributing.md: Ensure set of linux dev dependencies is complete

js/modules/types/message.js

@@ -166,7 +166,7 @@ exports._mapAttachments = upgradeAttachment => async (message, context) => {
   const upgradeWithContext = attachment =>
     upgradeAttachment(attachment, context);
   const attachments = await Promise.all(
-    message.attachments.map(upgradeWithContext)
+    (message.attachments || []).map(upgradeWithContext)
   );
   return Object.assign({}, message, { attachments });
 };
@@ -356,7 +356,9 @@ exports.upgradeSchema = async (
 
 exports.createAttachmentLoader = loadAttachmentData => {
   if (!isFunction(loadAttachmentData)) {
-    throw new TypeError('`loadAttachmentData` is required');
+    throw new TypeError(
+      'createAttachmentLoader: loadAttachmentData is required'
+    );
   }
 
   return async message =>
@@ -367,6 +369,36 @@ exports.createAttachmentLoader = loadAttachmentData => {
     });
 };
 
+exports.loadQuoteData = loadAttachmentData => {
+  if (!isFunction(loadAttachmentData)) {
+    throw new TypeError('loadQuoteData: loadAttachmentData is required');
+  }
+
+  return async quote => {
+    if (!quote) {
+      return null;
+    }
+
+    return {
+      ...quote,
+      attachments: await Promise.all(
+        (quote.attachments || []).map(async attachment => {
+          const { thumbnail } = attachment;
+
+          if (!thumbnail || !thumbnail.path) {
+            return attachment;
+          }
+
+          return {
+            ...attachment,
+            thumbnail: await loadAttachmentData(thumbnail),
+          };
+        })
+      ),
+    };
+  };
+};
+
 exports.deleteAllExternalFiles = ({ deleteAttachmentData, deleteOnDisk }) => {
   if (!isFunction(deleteAttachmentData)) {
     throw new TypeError(
@@ -392,7 +424,7 @@ exports.deleteAllExternalFiles = ({ deleteAttachmentData, deleteOnDisk }) => {
         quote.attachments.map(async attachment => {
           const { thumbnail } = attachment;
 
-          if (thumbnail.path) {
+          if (thumbnail && thumbnail.path) {
             await deleteOnDisk(thumbnail.path);
           }
         })