Change the type of the properties used to specify the input / output locations of {Merging,Splitting}Transformer
from vector-of-string to the more appropriate vector-of-DataObjID

See merge request !1298

Closes #114

See merge request !1296

See merge request !1293

See merge request !1288

See merge request !1291

See merge request !1289

Closes #212

See merge request !1290

Apply the `OrderedSetSemantics` by default to `std::unordered_set` and
`set::set`. This fixes e.g. problems when merging the
ExtraInputs/Outputs properties of algorithms.

See merge request !1287

See merge request !1286

See merge request !1285

See merge request !1284

See merge request !1282

See merge request !1279

The `TObject::InheritsFrom` call can be quite slow. Since we already
deduce the object type (`TH1`, `TTree`, etc.) during registration, save
this information and use it instead of re-deriving it every time.
Also avoid calling `updateFiles` if no TTrees are registered.

Both these changes significantly speed up the `EndEvent` incident
handling for jobs with large (>10k) number of histograms.

Also re-organize `struct THistID` to avoid padding and delete unused
`reset` method.