Added support for a retry interval to monitors

If a check fails and retries are used you can now specify a specific value for that. So you can check faster if the site goes back up again.

src/languages/en.js

@@ -1,8 +1,11 @@
 export default {
     languageName: "English",
     checkEverySecond: "Check every {0} seconds.",
+    retryCheckEverySecond: "Retry every {0} seconds.",
     "Avg.": "Avg. ",
     retriesDescription: "Maximum retries before the service is marked as down and a notification is sent",
+    retryIntervalInactive: "Inactive",
+    retryIntervalDescription: "If retries are and used this value is greater then zero this interval will be used instead.",
     ignoreTLSError: "Ignore TLS/SSL error for HTTPS websites",
     upsideDownModeDescription: "Flip the status upside down. If the service is reachable, it is DOWN.",
     maxRedirectDescription: "Maximum number of redirects to follow. Set to 0 to disable redirects.",
@@ -64,6 +67,7 @@ export default {
     Port: "Port",
     "Heartbeat Interval": "Heartbeat Interval",
     Retries: "Retries",
+    "Heartbeat Retry Interval": "Heartbeat Retry Interval",
     Advanced: "Advanced",
     "Upside Down Mode": "Upside Down Mode",
     "Max. Redirects": "Max. Redirects",