"Objectify" bc_record, bc_event_cam etc.

[ghost]

Some important entities in code are implemented as struct and bare C functions with respective prefix in names. This is inevitable inconvenience in pure C projects, but we use C++ compiler and can have use its benefits.
More than that, such structs and their "methods" are often put to different files, and even more, the name of that file doesn't match anything, which makes it a headache to track things.
This prevents the feature developed for #160 to be effective, see https://github.com/bluecherrydvr/bluecherry-apps/blob/xml_status/server/bc-thread.cpp#L485

As i have said in #160, it is better to be done NOT in parallel with any other new features, to avoid merging problems. Also such rework shouldn't be targeting 2.2 stable branch. So it makes sense to implement as "last commit on 2.3" - when there's nothing planned for backporting to 2.2.