Update location field related messages at artifact definition

It is not clear for Bamboo users and/or admins (running Bamboo on windows) if they should use "/" slash or back slash "\" when adding path references. This problem is clearly observed when they need to set a path on artifact definition location field e.g. 

Suggestion:

Please change validation message from:

This entry cannot contain the character \

to something like:

This entry cannot contain the character \, please use / to reference subdirectlries

Regarding the same field, please add the information that it is possible to use absolute paths when using the "/" at the beginning. This behavior is not clear.