Bug 23246: (follow-up) Hardcoding tab position is not enough

Bug 23246: (follow-up) Hardcoding tab position is not enough

There are many conditions that determine the tab number for 'media'.
Translated into variables that hold the tabs count on each condition, it
is clear that '3' was not good enough:
            [%- holdings      = (SeparateHoldings)   ? 2 : 1
                notes         = (MARCNOTES || notes) ? 1 : 0
                acq           = (Koha.Preference('AcquisitionDetails')) ? 1 : 0
                frbr          = (FRBRizeEditions  && XISBNS) ? 1 : 0
                local_covers  = (LocalCoverImages && (localimages || CAN_user_tools_upload_local_cover_images)) ? 1 : 0
                media_tab     = holdings + notes + acq + frbr + local_covers
            -%]

This patch gets rid of the hardcoded value, adds an id to the 'media'
tab (i.e. 'media_tab') and uses JS to get the right index.

To test:
- Play with the different options governing those variables
=> FAIL: 3 is not always the 'media' tab
- Apply this patch
- Repeat your tests
=> SUCCESS: It always picks the 'media' tab
- Sign off :-D

Sponsored-by: American Numismatics Society
Signed-off-by: Maryse Simard <maryse.simard@inlibro.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>