implement global search in the html report - backend

Implement search box in a blue app header.

Generate JSON data:

• packages, files, classes, methods, tests

Split into several indexes (for smaller file size) as theoretical size is up to 40MB (200'000 objects per 200 chars).

Add "automatic" option (up to 10'000 elements).

Add options for:
<clover report>/<current>/<format>/<globalSearch scope="package,file,class,method,test|auto" limit="10000"/>

Add option for HtmlReporter:
--globalSearchScope=package,file,class,method,test|auto
--globalSearchLimit=10000

to choose which elements shall be searchable.