Prevent password managers to overwrite passwords in reseller / client and mailbox edit screen (fixes #4030)

- cleaned up some javascript

- mail accounts not locked when client locked
- mail account sending and receiving lock separated
- fixed error in query
- fixed wording to match separeted locks

Fixed: password match function blocked tabs incorrectly
Fixed: set focus on username input field threw an error if this field did not exist on a page

added .label + .value class for non-INPUT details in edit forms; changed class for measurement unit to .label -> better output + reduction of unnecessary non-breaking spaces

- Random password length: by default, generated passwords will have a length between 10 and 15 characters (instead of a fixed length of 10 characters).

Added missing strings in some templates to english transalations

Fixing the way some User Interface text was used. For the quota on a mailbox I added 'in MB' so that the user knows what units the quota is in.