New ACID test: image orientation

Systematic test of image orientation (`XDir` and `YDir`) and axis visibility (`axis off`)
Split test to cover inline code and external PNG

* imageOrientation_inline works as expected
* imageOrientation_PNG fails due to bug, unrelated to test
Fix inlining images in TikZ code
Merge pull request #422 from PeterPablo/ACID_new_test_imageOrientation

[ACID]New tests image orientation