Re-introduces separate Description and Instructions tab for mapper interface.

Fixes osm-tasking-manager2 issue 193. It still needs work to change the Start Contributing buttom on the Description panel to link to the Instructions pane.
The Description panel button currently does not work at all.
Duplicates project.instructions.mako as project.description.mako for working out a bug.
Changes instructions identifier to description.
Fixes the non working button on the description panel.
Finalizes new project.decription.mako page for Description tab
Restores the correct master branch main.css
Simplify gotoinstructions button wording and id
Make sure the description tab is active first
Remove duplicated project status info
Merge pull request #481 from pgiraud/issue193InstructionsTab

Issue193 instructions tab