Added file Vim like write behaviour on :w <path> command

:write followed with a path will behave like Vim. 

* The file will be created with the proper content.
* If the file specified already exist the operation is aborted.
* If the directory in the path specified does not exists, the operation is aborted.
* If the source tab is linked to a file, the focus is kept on the source tab. The new tab is created behind.
* If the source tab is not linked to a file, it will be replaced by a new tab with the new file content.