MessageList refactoring to remove duplicate code paths.
MessageList refactoring to remove duplicate code paths.

Message operations should be more consistent now, regardless of how
the messages are selected (long click, checkbox+Menu, future group selection).

This is a backport of the modifications made on the issue258 branch,
without the threading specific features (no new feature introduced).

gnebsy/k-9,dgger/k-9,farmboy0/k-9,sonork/k-9,herpiko/k-9,sonork/k-9,sanderbaas/k-9,deepworks/k-9,sanderbaas/k-9,tonytamsf/k-9,imaeses/k-9,jca02266/k-9,philipwhiuk/q-mail,philipwhiuk/k-9,sebkur/k-9,439teamwork/k-9,cketti/k-9,cooperpellaton/k-9,thuanpq/k-9,leixinstar/k-9,Valodim/k-9,imaeses/k-9,dpereira411/k-9,dhootha/k-9,nilsbraden/k-9,dhootha/k-9,vatsalsura/k-9,WenduanMou1/k-9,icedman21/k-9,torte71/k-9,k9mail/k-9,nilsbraden/k-9,gnebsy/k-9,cooperpellaton/k-9,dpereira411/k-9,GuillaumeSmaha/k-9,gilbertw1/k-9,roscrazy/k-9,indus1/k-9,XiveZ/k-9,moparisthebest/k-9,huhu/k-9,G00fY2/k-9_material_design,rtreffer/openpgp-k-9,dpereira411/k-9,gaionim/k-9,k9mail/k-9,rollbrettler/k-9,rishabhbitsg/k-9,CodingRmy/k-9,vasyl-khomko/k-9,tsunli/k-9,vt0r/k-9,cketti/k-9,github201407/k-9,farmboy0/k-9,suzp1984/k-9,sedrubal/k-9,konfer/k-9,mawiegand/k-9,CodingRmy/k-9,moparisthebest/k-9,KitAway/k-9,indus1/k-9,cooperpellaton/k-9,WenduanMou1/k-9,crr0004/k-9,sanderbaas/k-9,G00fY2/k-9_material_design,jberkel/k-9,imaeses/k-9,herpiko/k-9,cliniome/pki,nilsbraden/k-9,WenduanMou1/k-9,huhu/k-9,bashrc/k-9,Eagles2F/k-9,mawiegand/k-9,sebkur/k-9,denim2x/k-9,dgger/k-9,msdgwzhy6/k-9,suzp1984/k-9,sebkur/k-9,thuanpq/k-9,ndew623/k-9,moparisthebest/k-9,denim2x/k-9,tonytamsf/k-9,github201407/k-9,tsunli/k-9,vt0r/k-9,439teamwork/k-9,suzp1984/k-9,KitAway/k-9,deepworks/k-9,vasyl-khomko/k-9,philipwhiuk/q-mail,sonork/k-9,thuanpq/k-9,crr0004/k-9,crr0004/k-9,ndew623/k-9,mawiegand/k-9,GuillaumeSmaha/k-9,konfer/k-9,GuillaumeSmaha/k-9,icedman21/k-9,KitAway/k-9,jca02266/k-9,torte71/k-9,philipwhiuk/k-9,gaionim/k-9,bashrc/k-9,cliniome/pki,bashrc/k-9,roscrazy/k-9,tsunli/k-9,torte71/k-9,vatsalsura/k-9,rishabhbitsg/k-9,konfer/k-9,gaionim/k-9,tonytamsf/k-9,ndew623/k-9,farmboy0/k-9,jca02266/k-9,dhootha/k-9,deepworks/k-9,sedrubal/k-9,huhu/k-9,icedman21/k-9,denim2x/k-9,rtreffer/openpgp-k-9,cketti/k-9,msdgwzhy6/k-9,k9mail/k-9,herpiko/k-9,gnebsy/k-9,Eagles2F/k-9,leixinstar/k-9,github201407/k-9,jberkel/k-9,rollbrettler/k-9,rollbrettler/k-9,cliniome/pki,XiveZ/k-9,cketti/k-9,msdgwzhy6/k-9,gilbertw1/k-9,gilbertw1/k-9,vasyl-khomko/k-9,philipwhiuk/q-mail,XiveZ/k-9,dgger/k-9,leixinstar/k-9,439teamwork/k-9,Eagles2F/k-9