Updated icon downloading

- Added more checks to prevent panics (Removed unwrap)
- Try do download from base domain or add www when the provided domain
  fails
- Added some more domain validation checks to prevent errors
- Added the ICON_BLACKLIST_REGEX to a Lazy Static HashMap which
  speeds-up the checks!
- Validate the Regex before starting/config change.
- Some cleanups
- Disabled some noisy debugging from 2 crates.

.env.template

@@ -104,7 +104,8 @@
 ## Icon blacklist Regex
 ## Any domains or IPs that match this regex won't be fetched by the icon service.
 ## Useful to hide other servers in the local network. Check the WIKI for more details
-# ICON_BLACKLIST_REGEX=192\.168\.1\.[0-9].*^
+## NOTE: Always enclose this regex withing single quotes!
+# ICON_BLACKLIST_REGEX='^(192\.168\.0\.[0-9]+|192\.168\.1\.[0-9]+)$'
 
 ## Any IP which is not defined as a global IP will be blacklisted.
 ## Useful to secure your internal environment: See https://en.wikipedia.org/wiki/Reserved_IP_addresses for a list of IPs which it will block