Add interval search to work search panel

[craigsapp]

Currently only pitch searches are enabled on the work-page search panel. Add interval searching as well.

Example: polishscores.pl/?id=pl-wnifc--13846--001-043

[craigsapp]

Implemented with commit https://github.com/craigsapp/website-polish-scores/commit/3efd42f1847c7fbf31d53553346ea3ff250de57d

Example: search for melodic minor thirds using m3 in the new interval field:

https://polishscores.pl/?id=pl-wnifc--13846--001-043

Search for two rising thirds (major or minor) followed by a falling second with 33-2:

https://polishscores.pl/?id=pl-wnifc--13846--001-043