[FIX] web: better factorize debounced/input fields code

`DebouncedField` and `InputField` classes were not properly factorized,
some of the DebouncedField code had to be part of the `InputField`
class (which is a specialization of `DebouncedField`). Indeed the
`FieldText` class, specialization of `DebouncedField` class, was missing
properties which were part of `InputField` and was duplicating code
which was already defined in `InputField`.

For example, it was not possible to navigate out of text fields in
editable list views with the right/left keys as this was part of the
`InputField` class.

Note: the FieldTextHtmlSimple class was implementing the `commitChanges`
function differently than `DebouncedField` but this was in fact not
necessary. This is why documentation update has also been done for this
by this commit.