[os-OPNWAF] Add GUI Option to Enable/Disable HTTP/2

[rushstone]

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Is your feature request related to a problem? Please describe.
Currently, enabling HTTP/2 in os-OPNWAF requires uncommenting the following line in the configuration file ("/usr/local/etc/apache24/httpd.conf"):

#LoadModule http2_module libexec/apache24/mod_http2.so

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Describe the solution you'd like
I would like a checkbox or toggle in the os-OPNWAF GUI settings (e.g. under "Default Settings") that allows users to enable or disable HTTP/2 support with a single click.

Example:

[ ] Enable HTTP/2

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Describe alternatives you've considered

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Additional context