Remove "removed" packages per [1] for mate 1.5/1.6

Several packages have been removed in mate 1.5/1.6, see [1] for details.
Also found several other smallish issues. Details below.

mate-base/mate-1.5.0
Bump all the versions to >=1.5.0
Remove packages per [1]
Add bluetooth USE flag and add cond DEPEND on net-wireless/mate-bluetooth

mate-extra/mate-sensors-applet-1.5.1
Remove DEPEND:
>=mate-base/libmate-1.2.0
>=mate-base/libmateui-1.2.0

mate-base/mate-applets-1.5.1
Remove DEPEND mate-base/libmate
Also remove missed gtk-doc DEPEND
Fix below QA notice (flag moved to mate-media).
* QA Notice: Unrecognized configure options:
*
* 	--enable-mixer-applet

mate-base/mate-panel-1.5.5-r1
Bump version to 1.5.5-r1
Remove DEPEND:
>=mate-base/libmatecomponent-1.2.1
>=mate-base/libmatecomponentui-1.2.0
>=mate-base/mate-corba-1.2.2
Remove pkg_prerm and pkg_postinst (gsettings replaces mateconf)

mate-base/mate-file-manager-1.5.3
Remove DEPEND on >=mate-base/mate-vfs-1.4.0

[1] http://wiki.mate-desktop.org/status:1.6
mate-base/mate-1.5.0 Fix several DEPEND issues

Missed DEPEND removal for:
>=mate-base/mate-conf-1.5.0
>=mate-base/mate-mime-data-1.5.0

Also keep x11-term/mate-terminal at version 1.4.0 as version 1.5
still has issues.
Package mask =mate-base/mate-1.5*
Merge pull request #8 from infirit/mate_1.6_package_removal

Mate 1.6 package removal