docs: Fix typos and some wrong expressions in Eina API reference doxygen.
Summary: I had fixed some typos and some wrong expressions, such as capital letters, singular, and orders of groups in Eina API reference doxygen.
Test Plan: Doxygen Revision
Reviewers: stefan, cedric, raster, Jaehyun_Cho, jpeg
Reviewed By: jpeg
Differential Revision: https://phab.enlightenment.org/D4674