implement shell filter

[GorgonMeducer]

• set macro PIKA_SHELL_FILTER_ENABLE to 1 to enable the feature
• define macro PIKA_SHELL_FILTER_FIFO_SIZE to set the filter buffer size.
• add your default filters (string, array) to __default_filter_msg_table.cfg at compile-time
• register your filters to ShellConfig instance at runtime.