Feature/entities checker util

[jkshj21]

Hello Pat,

I worked on the entities checker util class that I presented to you in the last meeting. It has various functions that validate or output entity types related data of dfcx.

If you like this class then I'm planning to add more functions like:

• running a full entity regression test across all the pages; it checks match_type, matched value and triggeredCondition
• merging with the pages_df and the entity_types_df to provide an insight on where the entity types are

Josh Han (joohyong)

[kmaphoenix]

@MRyderOC tagging you for review. Thanks!