Lens.pm: change schema of search results according to https://wiki.ubuntu.com/Unity/Lenses#Schema
Lens.pm: write spec for category*() methods.
Lens.pm: refactor methods about "Results" Dee Model into Web::Dash::DeeModel module.
Lens.pm: implement category*() methods.
Dash.pm: results from search.json now includes "category" attribute. "category" attribute holds the category object which is joined on "category_index".
Dash.pm: render search results by categories. still need to brush up UI...
Dash.pm: complete basic styles.
Dash.pm: add list toggler when there are too many results in a category.
Dash.pm: fix the bug: clicking on lens radio button did not work because value of <input> is now the service name of the lens. Embed lens index to data-lens-index attribute of the <input>.