Add line_integral feature for abitrary fields

.gitignore

examples/channel_flow_force/input.yml

examples/channel_flow_pressure/input.yml

examples/knudsen_pump/input.yml

examples/knudsen_pump/study/input.yml

examples/lid_driven_cavity/input.yml

examples/lid_two_regions/input.yml

examples/thermal_edge_flow/input.yml

examples/thermal_edge_flow/input1.yml

examples/thermal_edge_flow/input10.yml

examples/thermal_edge_flow/input11.yml

examples/thermal_edge_flow/input12.yml

examples/thermal_edge_flow/input2.yml

examples/thermal_edge_flow/input3.yml

examples/thermal_edge_flow/input4.yml

examples/thermal_edge_flow/input5.yml

examples/thermal_edge_flow/input6.yml

examples/thermal_edge_flow/input7.yml

examples/thermal_edge_flow/input8.yml

examples/thermal_edge_flow/input9.yml