Refactoring roadmap

[Jalle19]

I'm opening this here instead of creating a PR so we can come to an agreement on what should be done and what not. There are a couple of issues I'd like to address:

• separate all classes into separate headers. Currently we have a bunch of .cpp files that all share the common (massive) Tvheadend.h header.
• add some getters to CTvheadend to retrieve e.g. the global CHTSPConnection object, this way we wouldn't need all the "passthrough" methods in CTvheadend (see the demuxer related methods for instance). => ksooo: not sure about this one. I think pushing stuff (context) down is to prefer over sharing a global tvh object from which everything can be pulled.
• move all classes under a tvheadend namespace as a separate subdirectory, and unify the naming scheme by dropping the C and CHTSP prefixes from our classes. => ksooo: only class CTvheadend left in global namespace after #334
• Use classes instead of structs for our internal objects (timers, channels, events) and add proper comparison operators to them in order to get rid of the UPDATE macro.
• attempt to separate the Kodi API as clearly as possible from the tvheadend namespace, this means that e.g. PVR_CHANNEL structs are not passed down from client.cpp. Instead, the corresponding channel is looked up and CTvheadend operates on SChannel (or a class Channel, see earlier point) instead.
• Replace CStdString
• replace C style casts with C++ style casts.

@ksooo do you agree with these points? If we decide to do this we should probably do it incrementally, starting from the top (separating classes into separate files) to keep the changes managable and reviewable.

[ksooo]

Full ACK to all points. :+1:, esp. for the incremental approach.

Not sure about the "separate subdirectory" for types in namespace tvheadend. What else will we have beside "tvheadend"?

[ksooo]

BTW, for the series recording stuff I already started not to squash everything into Tvheadend.[cpp|h]. ;-) => https://github.com/ksooo/pvr.hts/commits/series-recording-support

[ksooo]

One more todo: Get rid of CStdString, replace with std::string

[ksooo]

One more: Replace c casts with c++ casts

[Jalle19]

Not sure about the "separate subdirectory" for types in namespace tvheadend. What else will we have beside "tvheadend"?

This is just a habit of mine, I like having the directory structure reflect the code structure as well (having a folder per namespace is similar to having a file per class).

[Jalle19]

Just a heads up, I've started working on some of the stuff here

[Jalle19]

I've almost finished factoring out some non-connection related stuff from CHTSPConnection, I'll put up a new PR to replace the two existing ones.