Add `_` to some term constants for consistency.

Terms changed:
`CONCATMAP`
`ORDERBY`
`TYPEOF`
`FUNCALL`
`FOREACH`
`GEOJSON`
`TO_GEOJSON`
Revert change to `GEOJSON` terms.
Reverse method aliases in `func.rb` to maintain old methods.
Revert change to `FUNCALL` term.
Merge pull request #3147 from grandquista/grandquista/standard_term_name

Add `_` to some term constants for consistency.