luci-mod-network: add stricter wireless interface name validation

Linux wireless interface names have the following restrictions:

 * It must not be an empty string
 * It must not be '.' or '..'
 * It must not contain any /, : or space character ( , \t, \n, ...)
 * It must be less than 16 chars
 * It likely must not contain any % either

Fixes: 8673aef8

 ("luci-mod-network: remove uciname validation from wireless interface")
Signed-off-by: Glenn Washburn <development@efficientek.com>
[reword validation error messages, remove extended description text as it would be
 shown as part of the validation errors]
Signed-off-by: Jo-Philipp Wich <jo@mein.io>