plotter.ticks: fix bug in epoch checking

(cherry picked from commit 2ee1bc8d31e25d9ea750d05d82397bc996244532)
TimeSeries.psd: minor type casting fix

(cherry picked from commit 37dce675f1916a8b52335e4e2d7d43539a073052)
Series: bug fix in metadata ownership when slicing

(cherry picked from commit 13b5ee1db98618727b18794828e512088defa240)
Series: improved index property

(cherry picked from commit 73e5b33b805d2a27392b94910d937de4db09df74)
Array2D: improved index_x, index_y properties

(cherry picked from commit 5a91ea31635328b5936432c96c1bfd87ff6aca2a)
Array2D: now return span_x, span_y as Segment

(cherry picked from commit 800b79a2a1c7effd7a8cdb930e20a42baac8e35e)
Series: bug fix in index property

(cherry picked from commit 093660a1632929d9d48062c8a27183b05c3781dc)