Improve support for Syndetic Solutions Syndetics Classic

Evergreen currently supports the display of added content from Syndetic Solutions using an offering now known as Syndetics Classic.

For work on adding support for Syndetics Plus (not as a replacement for Syndetics Classic), see bug 1297614

There are a few areas where support for Syndetics Classic could be enhanced:

1. Recent changes to the HTML returned by Syndetics Classic have resulted in undesirable formatting glitches in the display of some textual data elements such as reviews and summaries. It may be desirable to transition from the HTML method to the XML method of obtaining these elements.

2. Currently, there is no way to add or remove Syndetics Classic data elements short of editing Syndetic.pm directly. By default, several review sources are requested which may not be included in a library's Syndetic Solutions account. This can affect performance.

3. There are methods of determining which Syndetics Classic data elements are available for a given lookup, but we do not currently make use of them. This can affect performance.

Items 2 and 3 are closely related.

For these reasons (and perhaps others not yet listed here), it may be desirable to transition to the XML method of accessing Syndetics Classic data elements, rather than the HTML method.

Depending on the results of some quick investigation, we may wish to spawn a smaller bug for cleaning up the known new HTML formatting issues, or that may be the method which is backported, while larger changes take a different form in an upcoming major version of Evergreen.