Keep track of availabilities and pre-fill viewings requests

[peterpeterparker]

Linked with #2

The idea is to keep track (in app storage) of the availabilities filled by the user and to pre-fill the next viewings requests with these

For example:

• User send a first viewings request to flatshare A for the 2nd and 3rd January at 7pm
• When user want to send a viewings request for another flatshare B, if these dates are also available and in the future, pre-fill them

This will helps users saves time