* drop c++14 requirements since it is not used
* move from enum to enum classes
* more intuitive graph building in GI
* allow X-AW-Direction property works with graphs and bars
The previous versions stored values as string, so any (even if they are
not used) values being converted into string, and then (if required)
being converted back to float/int/etc. I've changed the mechanism, so
they are stored as QVariant (native value).
Please note that it is possible that this rewrite may cause crash in
some cases (if I've missed smth).
I've added 'optimize' option (by default true). If it options is set
then sources will be checked if they are required (with dependencies if
any). And if they are not required they will be dropped by using common
mechanism.
Please note that if this option enabled the following features (at the
moment) will be unavailable:
* key request from context menu (from configuration interface it still works)
* notifications event if sources on which notification is not connected
I suppose this commit will increase performance in about 4-5 times.
