Форуми / Cotonti / Support / Input validation in Cotonti, and other

Here's what should be changed to get validated pages:
- Use & in URLs instead of just &. This will solve most of the validation errors.
- All system images should have alt tags.
- Javascript attributes in html tags should be lowercase instead of camelcase (onChange => onchange).
- Forum anchor ids should start with a letter instead of a number.