Follow up of PR #4: UI adjustements

Make the two new inputs fields on two columns.
Some code refactoring.
Changing how we get the field id

This commit is a manual pick of 68025a4177ba5d53e161afe76fef88678e4a81a9.

> We now use the key of the array returned by $section->fetchFields();
Fix release date, author url and compatible versions
Some refactor to allow formats in the anchor label

This change refactors how string are formatted.
This change also reuses the code to format the anchor label.
markdown format
apply format on anchor label in publish page too
Added root, workspace and http-host system params

As per #8, those new params can be accessed usign
{$system:root}, {$system:workspace}, {system:http-host},
added doc about system params
1.2 release notes
Merge pull request #2 from DeuxHuitHuit/master

Update to 1.2