Renamed Images/ to images/

This'll definitely break images when deployed but local builds (on OS X) won't show any difference since HFS+ is case insensitive
Updated image URLs in "An Introduction to Coasts" article
Updated image URLs in the "Waves" article
Updated image URLs in the "Tides" article
Updated image URLs in the "Coastal Erosion" article
Updated image URLs in the "Features of Erosion" article
Updated image URLs in the "Features of deposition" article
Updated image URLs in the "Coastal Management" article
Updated image URLs in the "Population Structure" article
Updated image URLs on the credits page
Updated image URLs in the "Drainage Basins and the Hydrological Cycle" article
Updated image URLs in the 'Discharge and Hydrographs' article
Updated image URLs in the 'River Processes' article
Updated image URLs in the 'Long and Cross Profiles' article
updated image URLs in the 'River Landforms' aritlce
Updated image URLs in the 'Rejuvenation' article
Updated image URLs in the 'Flooding' article
Updated image URLs in the 'Flood Management' article