Bug 17380: Do not allow Default template in merge form

Bug 17380: Do not allow Default template in merge form

This patch makes the following changes:
[1] Removes Default from the template list. We should not merge with the
    Default framework, since it does not have a reporting tag.
[2] Rearranges the error section in the template. It is confusing to have
    two error sections in this template. The error CANNOT_MOVE is not used.
    The error FRAMEWORK_NOT_SELECTED is replaced by WRONG_FRAMEWORK.
[3] Do not allow to merge a record with itself.
[4] Check if the merge reference record still contains any MARC tags.
[5] Additional polishing: Simplify passing frameworks to template. Remove
    an unused Koha::Authority::Types->search. Remove obsolete POD header
    for functions from the script.

Test plan:
[1] Select two authorities to merge. Verify that you cannot select Default
    anymore as framework for the reference record.
[2] Reproduce error WRONG_COUNT by adding another authid=999 in the URL
    after you selected two authority records for merging.
[3] Remove the third authid from the URL and change the first or second
    authid into an unexisting record id. You should generate an Internal
    Server Error. The log should show the exception message.
[4] Merge two authorities. Deselect all MARC tags. Should trigger the
    error EMPTY_MARC in the template.
[5] Select the same authority record twice for merging. Should trigger the
    error DESTRUCTIVE_MERGE in the template.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>