Flag filter

[ChrissW-R1]

Added option to control the flags in popups by a new flag called dynmap-flags-filter. So you could control, which information are public on the online map.

Usage:
The flag should contain a comma-separated (,) list of flags with the information to show it, separated by an colon (:).
Eg.: dynmap-flags-filter=greeting:allow,farewell:deny, will show the greeting and hide the farewell flag.

Also some configuration options were added to control the behavior of this feature.

# Filter region flags in info window
flag-filter:
  # Enable the flag filter feature
  enable: true
  # Should the flags hidden by default
  hidden-by-default: false

If the configuration is not changed, everything remains consistent.

[ChrissW-R1]

Solves #71