Allow Conditions Where Custom Block Can Appear

[antelmoa]

In Drupal, there is also a Block concept very similar to OJS. In the interface for Blocks in Drupal, one can select in what pages/urls the block can appear or not appear. I believe it would be useful to have this feature implemented for this plugin as well. I know that I had this requirement where I needed to display a block in certain pages. Right now I just hide it with CSS, but the better solution is to have this configuration in the Custom Block form.