Added feature to calculate hospitalised injuries in time and udate occupants due to injuries and repair (applied to RLA only so far)

The new feature:

• Defines a timeline of injured people still unable to return to their buildings due to their health status (irrespective of the damage state of their buildings).
• Defines a timeline for people being allowed back into their buildings as a function of the time (number of days) it takes to inspect and repair them.
• Stores the above in terms of UTC, per earthquake.
• Updates the number of occupants in the buildings when running each earthquake.

Associated changes/additions needed for the above:

• Changed handling of occupants from requiring columns of day, night and transit occupants in the exposure files to requiring only a census column and a series of factors (used to multiply the census values to obtain the day, night and transit values) defined in the config.yml file and, consequently, the Configuration class.
• Changed the logic of the updating of the exposure model: after each earthquake, it updates the number/proportion of buildings in each damage state, and distributes replacement costs and number of census occupants proportionally, and this is how the "current" exposure is stored. Right before running the next earthquake, it looks at the UTC and time of the day of the new earthquake, retrieves the number of people still unable to go back to their buildings (either due to death, injury, time to inspect or time to repair), and calculates the number of occupants at the time of the earthquake that has "just occurred".

All of the above has so far only been applied to RLA. Application to OELF will follow.