Improvements and fixes

Negative days no longer distort the dashboard's energy bars, and a data logger's login details can be edited from the components page.

• A day that works out negative now shows as 0 in the dashboard's energy bars, with the amount carried over against the following day.
• A data logger's login details can now be changed in its details on the components page.
• Through the API, adding a ticket comment longer than 10,000 characters is now rejected with a validation message instead of failing with an unexpected error.