Check filepath lowercased and hyphenated

[jinmiyoon]

We currently check filenames only, but we also require all subdirectory names compliant with lowercase letter and hyphenated. It should flag as FAIL when filepath strings include uppercase letters or underscored or other types of non-allowed special characters.

For example, the folder name using target name like v26/70_Ohi_B should be v26/70_ohi_b.