Remove "libraries" dependency

[smaiorana]

The REST Server submodule has a dependency on the Libraries module, even though Libraries has been deprecated. If you install Services and REST Server together on a Backdrop instance that doesn't already have Libraries installed, it crashes the install process with a 500 error due to a missing call to libraries_detect().

Since Libraries has been deprecated and the "spyc.php" library is packaged with the Services anyway, the Libraries dependency should be removed.

[smaiorana]

I submitted PR #9 to resolve this issue. Ran a brief test of a call expecting a YAML response and it seemed to work fine.

[smaiorana]

On second look, it appears the 500 error I experienced was unique to one particular Backdrop instance. I was operating from a forked version of the Libararies module that was used to help facilitate a Drupal-to-Backdrop migration. A typical Backdrop installation should not experience the same error I encountered.

That said, the Libraries module has been deprecated and its documentation states:

NOTE: The Libraries API contrib module has been deprecated, as equivalent functionality has been added to Backdrop core. This module will not receive any further updates.

If a module you're trying to use depends on Libraries API, please suggest to the module maintainer that they update their module to use core's library functions instead.

So take this as my suggestion 😄

The PR I submitted should still accomplish removal of the dependency.

[smaiorana]

I just updated this PR to eliminate any additional tests and download directives related to the spyc library.