Display index page for Tools > Import/Export > Crossref XML Export Plugin

[bozana]

Describe the Bug:
When going to Tools > Import/Export > Crossref XML Export Plugin an exception is thrown. Instead display the index.tpl page with further information, where to find the new settings and export possibilities.

Using OJS 3.4

PRs:

• pkp/crossref-ojs#32 display index page and fix issn requirement #33
• pkp/crossref-ojs#32 submodule update ##bozana/32## ojs#3880 (only submodule update)

[bozana]

@ewhanson, could you please take a look at the PR above?

[jonasraoni]

Please, check if it's the same issue:
pkp/pkp-lib#8838

[bozana]

Oh yes, it is... I will then also fix the DataCite and move everything (the PRs) over there -- I found it is also generally better/easier to follow issues there in pkp-lib...
Thanks!