Review usage of vh units on Web UI

We must review the usage of vh units for sizing the height of elements in Web UI, since it causes elements to be larger they the are intended to. This is causes by a known issue that affects most mobile browsers. A proposal for a new unit that takes this into account is in progress. Current possible workarounds consist of:

• using percentage units
• leveraging the solution used in NXP-27429 and make it more generic, making nuxeo-app recompute the --vh variable on resize, so it can be used on other elements (approached described here).