[ImgBot] Optimize images

*Total -- 1,920.20kb -> 1,549.73kb (19.29%)

/doc/_static/images/ccbysa.png -- 4.96kb -> 1.59kb (67.89%)
/doc/contraction/images/undirected_sampledata_a.png -- 24.47kb -> 8.37kb (65.81%)
/doc/_static/images/pgrouting-logo.png -- 18.84kb -> 12.47kb (33.8%)
/doc/_static/images/developers/disconnectEdgeUndirected.png -- 4.30kb -> 2.98kb (30.59%)
/doc/_static/images/developers/disconnectEdgeDirected.png -- 4.52kb -> 3.22kb (28.72%)
/tools/testers/solomon100-optimal.png -- 128.14kb -> 95.99kb (25.09%)
/doc/contraction/images/sample_graph_with_shortcuts.png -- 54.12kb -> 41.01kb (24.22%)
/doc/traversal/images/bfs-ascending.png -- 61.92kb -> 47.40kb (23.45%)
/doc/images/Fig1-originalData.png -- 101.35kb -> 78.26kb (22.78%)
/doc/coloring/images/bipartite.png -- 34.39kb -> 26.64kb (22.54%)
/doc/traversal/images/bfs-descending.png -- 63.25kb -> 49.06kb (22.43%)
/doc/lineGraph/images/original.png -- 24.18kb -> 18.76kb (22.41%)
/doc/withPoints/images/rightDrivingSide.png -- 84.26kb -> 65.49kb (22.27%)
/doc/withPoints/images/leftDrivingSide.png -- 83.56kb -> 65.13kb (22.05%)
/doc/components/images/bridge_sampledata.png -- 48.80kb -> 38.04kb (22.05%)
/doc/images/Fig2-cost.png -- 50.16kb -> 39.15kb (21.95%)
/doc/planar/images/nonPlanar.png -- 58.64kb -> 45.93kb (21.67%)
/doc/contraction/images/undirected_sampledata_c.png -- 49.37kb -> 38.96kb (21.08%)
/doc/withPoints/images/noMatterDrivingSide.png -- 50.79kb -> 40.19kb (20.86%)
/doc/components/images/ap_sampledata.png -- 28.81kb -> 22.87kb (20.6%)
/doc/images/Fig6-undirected.png -- 25.92kb -> 20.66kb (20.29%)
/doc/contraction/images/sample_graph.png -- 25.92kb -> 20.66kb (20.29%)
/doc/images/Fig4-costUndirected.png -- 26.00kb -> 20.83kb (19.9%)
/doc/lineGraph/images/transformation.png -- 127.76kb -> 103.72kb (18.82%)
/doc/images/with_restrictions.png -- 124.76kb -> 102.16kb (18.11%)
/doc/tsp/images/wi29Solution.png -- 38.41kb -> 31.86kb (17.05%)
/doc/contraction/images/newgraph.png -- 50.23kb -> 42.38kb (15.62%)
/doc/components/images/cc_sampledata.png -- 59.32kb -> 50.97kb (14.09%)
/doc/contraction/images/undirected_sampledata_b.png -- 41.98kb -> 36.65kb (12.71%)
/doc/components/images/bcc_sampledata.png -- 62.21kb -> 54.36kb (12.62%)
/doc/traversal/images/Fig2-DescendingOrder.png -- 52.23kb -> 45.69kb (12.53%)
/doc/traversal/images/Fig1-AscendingOrder.png -- 51.58kb -> 45.24kb (12.3%)
/doc/src/images/touching_edges.png -- 27.77kb -> 24.50kb (11.75%)
/doc/src/images/crossing_edges.png -- 39.69kb -> 35.12kb (11.5%)
/doc/images/restrictions.png -- 70.42kb -> 63.51kb (9.81%)
/doc/src/images/Dijkstra_Animation.gif -- 8.84kb -> 8.15kb (7.77%)
/doc/components/images/scc_sampledata.png -- 73.94kb -> 69.31kb (6.26%)
/doc/tsp/images/wi29optimal.png -- 34.38kb -> 32.42kb (5.7%)

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