Add high level terms to phenotype filter

[jseager7]

Currently the phenotype filter on the gene pages only filters by PHIPO phenotype, but we'd like the high level terms to be available for filtering too.

The high level terms can be shown in the same <select> drop-down as the other phenotypes, with the high level terms and PHIPO phenotypes separated by <optgroup> elements.

Here's a mockup for the PHI Phenotype section of PHIG:253:

Here's some example HTML for the above image:

<select>
  <option>Filter by Phenotype</option>
  <optgroup label="High level terms">
    <option >Reduced virulence</option>
    <option >Unaffected pathogenicity</option>
  </optgroup>
  <optgroup label="Phenotypes">
    <option>pathogen-induced host phenolic compound present</option>
    <option>absence of host seed development induced by pathogen</option>
    <option>abolished pathogen tissue to tissue migration within host</option>
    <option>pathogen-induced host phenolic compound absent</option>
    <option>presence of pathogen-associated host lesions</option>
    <option>decreased extent of pathogen-associated host lesions</option>
    <option>presence of pathogen tissue to tissue migration within host</option>
    <option>pathogen deoxynivalenol within host absent</option>
    <option>pathogen deoxynivalenol within host present</option>
  </optgroup>
</select>

---

If there are no high level terms for a section, then the <select> element should appear without any <optgroup> elements. Basically, the drop-down should appear as it did before the above change. Here's an example for PHIG:253:

[jseager7]

Confirmed that the implementation works as expected.