ladspa: nicer element names, especially for Linux Studio Plugins

This MR changes the element names of LADSPA plugins slightly (and majorly for LADSPA plugins from the Linux Studio Plugins collection).

As such, it is a breaking change, but seems somewhat worthwhile, and the names weren't stable across different OS anyway, so it actually fixes something, arguably.

commit 9e6267a2:

ladspa: element name clean-up: don't include ladspa plugin suffix in factory name
  ladspa-filter-so-hpf -> ladspa-filter-hpf
  ladspa-filter-so-lpf -> ladspa-filter-lpf
  ladspa-delay-so-delay-5s -> ladspa-delay-delay-5s

etc.

commit f2febaac:

ladspa: element name clean-up for LADSPA Linux Studio Plugins
Add some code to not create ridiculous element factory names for
the Linux Studio Plugins LADSPA plugins. Can be extended later
for other LADSPA plugin origins as well.

e.g.:

  ladspa-lsp-plugins-ladspa-http---lsp-plug-in-plugins-ladspa-sc-mb-compressor-ms -> ladspa-lsp-sc-mb-compressor-ms
  ladspa-lsp-plugins-ladspa-http---lsp-plug-in-plugins-ladspa-oscillator-mono -> ladspa-lsp-oscillator-mono
  ladspa-lsp-plugins-ladspa-http---lsp-plug-in-plugins-ladspa-gate-stereo -> ladspa-lsp-sc-gate-stereo