Allow non-text arguments to net_download

This checks the type of each query value to see if a cast to string is
necessary, which is required by the surrounding quote() call.
Introduce new util_split() service method

This new utility method will let a service split apart a long blob of
text intelligently if it exceeds a limit imposed by the service.
Change net_download() to support multiple targets

This now allows a service to call into a service with the result being
that all files get glued together.
Port Google to support long phrases

This also adds support for textlen, idx, and the like.
Break on question marks also

Treats these the same as periods.
Port Yandex.Translate to long phrase support

This is similar to Google, but with fewer parameters.
Improve intelligent splitting support

Adds support for some Asian languages and prioritizes spaces above word
separators.
Shorten up service implementations

Allows all calls to run through util_split, simplifying the code paths.
Services to keep track of download counts

This is done in the underlying net_download() function, so service
implementations do not need to do this directly.
Clarify throttling configuration

Rephrases the configuration screen's throttling section to explain what
it is used for (i.e. batch processing and not usual add-on usage).
Pass download count with the miss callback

When a cache miss occurs, wait to call the callback until after the
service run completes; at that point, call the callback and pass the
download count so it can count against the throttling.
Update help documentation for MP3s config

Adds discussion about services requiring multiple downloads for a single
input phrase and updates the screenshot.
Merge branch 'bug/downloader-21' into develop

Brings in support for long phrases for Google Translate and
Yandex.Translate. Closes #21.