New permission to acces all informations of subprojects of a project (Feature #831)

Hi, in my company we need a relay role for each Business Unit.
This role must have access to all sub-projects issues, wikis, documents, etc.

This responds to the need to have an account which can be used to have access to all the sub-projects informations of the Business Unit.
This is really useful in the case where the project leader and the project developers are not available, and the customer need to have a reply to a question related to the project (answer that often can be found in the Redmine tickets of the project).

The new permission for this role will be called See Sub-projects

ATTENTION: An user can only have once this new role. :
It's in the first role found that has this permission See Sub-projects that we get the project (the Business Unit) on which the member will have access to all the sub-projects.

The new permission has been translated in fr, en, es and uk(rainien).

We have developed an enhancement (that does not need much changes) and are testing it during next January. We will provide a patch as soon as the enhancement will be validated inside our company.

C.f. http://www.redmine.org/issues/9878