added param DatabasePath to Create-Database

Added a parameter "DatabasePath" to Create-Database where you can
overwrite the default setting where the database files (data and log)
should be placed when creating a new database.
DatabasPath param: removed creating directory

since the database can be hosted remotly, creating the directory on the
machine where the scrupt is running makes no sense
Merge pull request #7 from unic/master

added param DatabasePath to Create-Database