writerfilter: refactor to get rid of savedPositionOffset{V,H} statics

Which are extremely scary, allowing a shape position from one doc to
appear in an other if two writerfilter import is in progress at the same
time.

This partially reverts 8fa1a0874765ea7db57e496f1d92731b9ab09280 (read
wp:positionOffset, wp:alignV and wp:alignH properly (bnc#513579),
2011-05-04).

Change-Id: I0fcddf88fa56f5f9288e47bcd100c38ee9cf2f13
writerfilter: refactor to get rid of remaining scary PositionHandler statics

Change-Id: I954504ad6b730866504a470b8d966fdfe1d58550
TagLogger is used only in dmapper

Change-Id: Ic88909ded4a28b1c019a03eefdaf3716cfbe9079
writerfilter: hardcoded cFieldStart/Sep/End

Change-Id: If7278418e1c7f8b8f812ce0b01720f8666e9ae5a