Fix cooling bug

Gas particles no longer cool below the energy floor if the timestep increases.

Changed CoolingHaloWithSpin example so that gas particle masses are more sensible.

Added 2 commits:

• 23f1178d - Code formatting
• 2c32b1e7 - Extended the modifications to the other schemes.

Status changed to merged

mentioned in commit 4d592c18

Works so accepted. Thanks.