add basic update functionality

If enabled, jfa-go pings buildrone (hosted at builds.hrfee.pw) every 30
min for new updates. If there is one, it gets information (and if
applicable, a binary) from the appropriate source (buildrone, github, or
dockerhub) and displays it on the admin page. You can switch update
channels between stable and unstable. For binary releases, updates are
downloaded automatically and installed when the user presses update.

Since this obviously introduces some "phone-home" functionality into
jfa-go, I just want to say IPs are not and will not be logged by
buildrone, although I may later introduce functionality to give a rough
idea of the number of users (again, no IPs stored). The whole thing can
also be turned off in settings.

lang/admin/en-us.json

@@ -24,6 +24,9 @@
         "enabled": "Enabled",
         "disabled": "Disabled",
         "admin": "Admin",
+        "updates": "Updates",
+        "update": "Update",
+        "download": "Download",
         "lastActiveTime": "Last Active",
         "from": "From",
         "user": "User",
@@ -93,6 +96,7 @@
         "saveEmail": "Email saved.",
         "sentAnnouncement": "Announcement sent.",
         "setOmbiDefaults": "Stored ombi defaults.",
+        "updateApplied": "Update applied, please restart.",
         "errorConnection": "Couldn't connect to jfa-go.",
         "error401Unauthorized": "Unauthorized. Try refreshing the page.",
         "errorSettingsAppliedNoHomescreenLayout": "Settings were applied, but applying homescreen layout may have failed.",
@@ -115,7 +119,11 @@
         "errorFailureCheckLogs": "Failed (check console/logs)",
         "errorPartialFailureCheckLogs": "Partial failure (check console/logs)",
         "errorUserCreated": "Failed to create user {n}.",
-        "errorSendWelcomeEmail": "Failed to send welcome email (check console/logs)"
+        "errorSendWelcomeEmail": "Failed to send welcome email (check console/logs)",
+        "errorApplyUpdate": "Failed to apply update, try manually.",
+        "errorCheckUpdate": "Failed to check for update.",
+        "updateAvailable": "A new update is available, check settings.",
+        "noUpdatesAvailable": "No new updates available."
     },
     "quantityStrings": {
         "modifySettingsFor": {