Enhanced capabilities for config objects

[AndreLouisIssa]

on config_file:

• (ergonomics) get an existing binding by section and key directly (no creating a config_definition to pass into the __index metamethod of entries)
• (ergonomics) safe bind bind an entry, even if it already exists, and if so, replace the previous entry with the new information.

'ergonomics' features can be accomplished by combining the existing functions, but dedicated functions for them would be easier to use.

[xiaoxiao921]

Updated post to reflect current progress.