[Feature] Detecting if DBC path is valid

[BAndysc]

Is your feature request related to a problem? Please describe.
Currently user can put any path in DBC textbox and WDE will silently fail if the path do not contain valid DBC.

Describe the solution you'd like
Before saving, it should try to detect if path contains valid dbc. Checking for required files (without looking into the content) is enough.