maliit-plugins: Clean up recipe and add missing RDEPENDS

The following errors are only shown when started from console, also there are no visible errors during execution.
Error fixed: QML Image: Error decoding: file:///usr/share/maliit/plugins/org/nemomobile/icon-m-input-methods-shift-lowercase.svg

: Unsupported image format

This is unaffected from whether libqtsvg4 is installed or not.

Signed-off-by: Samuel Stirtzel <s.stirtzel@googlemail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>