Add optional annotations for field/container names in Inlet

Nobody has claimed this yet.

Inlet users may wish to annotate names of fields or containers, for example:
* *deprecated* fields that should result in a warning when used
* *renamed* fields that accept either the old or the new name

One way of implementing this without significantly changing Inlet's interface might be to introduce a lightweight AnnotatedName class:

```cpp
Table::addInt(AnnotatedName name, std::string description);
// ...all the other add* functions

class AnnotedName
{
AnnotedName(std::string); // implicit conversion for un-annotated names
static AnnotatedName deprecated(std::string deprecated_name, std::string message);
static AnnotatedName renamed(std::string old_name, std::string new_name);
};

// could be used like:
addInt("foo", "descr"); // normal
addInt(AnnotatedName::deprecated("foo", "we don't use this anymore"), "descr");
addInt(AnnonatedName::renamed("foo", "bar"), "descr"); // renamed foo -> bar
```

This might require a bit of refactoring (especially to perform multiple lookups for the same field in the input file), but should only affect a few parts of the internal implementation.

Start by locating Inlet's Table::add* functions and the internal input-field lookup implementation. Review how field and container names are currently stored and resolved, then determine how annotations could preserve the existing interface. Done should include deprecated-name warnings and renamed-name support, including lookup of both old and new names.

Written by the indexing model from the issue text.