html2js: add templatePathReplaces attribute for renaming template paths

This patch implements another config option to the html2js preprocessor,
namely it allows the user to transform paths via a list of regexps,
instead of passing the cacheIdFromPath callback.

The reason passing that callback is complicated is that it already
has some functionality (prependPrefix and stripPrefix), which would have
to be reimplemented in the user supplied callback, which is further
complicated by the fact that those are stored in the closure hidden from
the callback function.

Signed-off-by: Adam Golya <golya@balabit.com>
Signed-off-by: Balazs Scheidler <bazsi@balabit.com>