[Feature Request] Naming consistency suggestion in the .xlsx files

[Hannah-Doerpholz]

Is your feature request related to a problem? Please describe.
In all .xlsx files (investigation, study and assay) there is a "metadata" section describing identifier, title, description...
In both the study and assay file the section is titled STUDY METADATA and ASSAY METADATA, while in the investigation file it is only called INVESTIGATION.

Describe the solution you'd like
Maybe change the section title INVESTIGATION in the isa.investigation.xlsx file to INVESTIGATION METADATA for consistency.

[Hannah-Doerpholz]

Since INVESTIGATION is already defined by the ISA-tab specification, maybe we should change STUDY METADATA and ASSAY METADATA to only STUDY (as it it in the investigation file) and ASSAY