prevent user from creating or renaming sth. to an existing filename

- show tooltip when violating naming constraints while typing
- when target filename exists on server fallback to dialog to interrupt the users flow because something unexpected went wrong
- fixes #5062
- also fixes some whitespace and codestyle issues in files js
- uses css selector over filterAttr in touched js files

tested in chrome and IE8:
![bildschirmfoto vom 2013-10-22 17 19 42](https://f.cloud.github.com/assets/956847/1382993/185604b4-3b36-11e3-8759-b84da2f2b0de.png)
![bildschirmfoto vom 2013-10-22 17 19 18](https://f.cloud.github.com/assets/956847/1382994/188832c2-3b36-11e3-8fb8-f828bde85705.png)
![bildschirmfoto vom 2013-10-22 17 19 54](https://f.cloud.github.com/assets/956847/1382995/188e90c2-3b36-11e3-9f90-4d9160d59c3d.png)
![bildschirmfoto vom 2013-10-22 17 19 07](https://f.cloud.github.com/assets/956847/1382996/189091c4-3b36-11e3-816c-0d647ee827d4.png)
![bildschirmfoto vom 2013-10-22 17 23 02](https://f.cloud.github.com/assets/956847/1382998/193b7f4e-3b36-11e3-949a-47618af00ba1.png)

@jancborchardt @PVince81 @ser72 @DeepDiver1975 please review