update state syntax

[tsl0922]

Syntax:

#@state=<expr> is an improved version of #@prop:check to extend support for other state like disabled.

<expr> is like the profile-cond option in Conditional auto profiles, but it should return valid state string seprated by , (checked/disabled/hidden).

The code for other keywords is refactored to reuse the watch logic of <expr>.

#@prop:check is not suppored anymore.

Usage

_           ignore                                 #menu: Disabled #@state='disabled'
_           ignore                                 #menu: Checked #@state='checked,disabled'

Ctrl+s      stop                                   #menu: Stop #@state=playlist_playing_pos==-1 and 'disabled'
m           cycle mute                             #menu: Mute #@state=(mute and 'checked')

[tsl0922]

ping @zhongfly @hooke007 @verygoodlee