{{input}} helper with bindings are now recognized in child helpers

Passing bindings to helpers `{{inputField}}`, `{{hintField}}` and `{{labelField}}` work fine. However, it is does not work when they are passed to the `{{input}}` helper. This PR solve this issue. `prompt` and `placeholder` passed as bindings to `{{input}}` will be pass to `{{inputField}}` as binding. Idem for hint and label. For example `hint` passed as binding to `{{input}}` will be pass as `text`binding to `{{hintLabel}}`. Same pattern for label.

Tests have been added and they pass. 

README has been modified as well.

This reverts commit f5f2be5984eff3a22c67c9600fffcd76384d002a.