Add comment options to the alternate chain spec configuration

Added alternate chain specification options for the given constants from config.hpp:

• HIVE_MIN_ROOT_COMMENT_INTERVAL: min_root_comment_interval in the alternate chain spec object
• HIVE_MIN_REPLY_INTERVAL (and HIVE_MIN_REPLY_INTERVAL_HF20): min_reply_interval in the alternate chain spec object
• HIVE_MIN_COMMENT_EDIT_INTERVAL: min_comment_edit_interval in the alternate chain spec object
• WITNESS_CUSTOM_OP_BLOCK_LIMIT: witness_custom_op_block_limit in the alternate chain spec object

All of the above properties are optional and should contain the number type if specified.

All of the properties describe the given interval in seconds