Rename assay files

[eamonnmag]

should we allow 'on the fly' renaming to avoid editing outside ISAcreator (issue is saving new files with new names and deleting old files with old names from the folder holding the ISA archive)
(request by Hanna Cwiek)

[sneumann]

+1 the request from Hanna Cwiek

[maciej-jonczyk]

+1 from me also. Now renaming requires manual changing of Assay and Study names in i_investigation.txt file and manually renaming of a_assay.txt and s_study.txt files themselves.