Add new JAR to Bio-Formats downloads page (rebased onto dev_4_4)



This is the same as gh-47 but rebased onto dev_4_4.

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This PR:
- adds the new `bioformats_package.jar` to the principal downloads table 
- replaces the Bio-Formats icons used the new ones designed by @gusferguson
- adds the zipped API documentation to the downloads page

Closes #37